Sector review – stochastic sample slice sequencer from Jonatan Liljedahl/Kymatica

Download from iTunes App Storesector logoOK, let’s start with the obvious question….  just what the heck is a stochastic sample slice sequencer? While it might be the kind of gizmo that finds its way on to a planetary geologist’s fantasy unmanned Mars rover, fortunately for us (well, unless you happen to be a geologist with an interest in other planets), in Sector’s case, it is a tool for manipulating audio loops.

The ‘sample slice’ bit is straightforward enough; Sector allows you to take an audio loop an slice it into….  well….  slices….. except that in Sector speak, these are ‘sectors’ and you can divide your loop into anything between 2 and 32 of these sectors. The ‘sequencer’ bit is also – in principle at least – straightforward as it then allows you to build new loops by reassembling the sectors in a new order. So far then, we are dealing with the same sort of technology that underlies long-established beat-slicing techniques, as originally perfected in Propellerhead’s ReCycle and their REX2 file formats, but subsequently mimicked in almost all the major desktop DAWs.

Sector's main Map screen - with the rather beautiful central loop display and the app running within Audiobus. Markov Chain statistics anyone?

Sector’s main Map screen – with the rather beautiful central loop display and the app running within Audiobus. Markov Chain statistics anyone?

But what about the ‘stochastic’ bit? For those of you without a PhD in statistics (er….  that’s all of us then), a stochastic process is something that has a random element to it and, if not purely stochastic, its behaviour is, in part, controlled by probabilities. In Sector, this random/probability-driven element of its behaviour operates at two levels; first, it determines (and adds variation to) the order in which the different slices (sectors) of your loop are played back and, second, it can be used to change the processing applied to a slice (sector) when it is played back by applying various ‘warp effects’ to the slice.

The app allows you to adjust the various probabilities applied to both these stochastic elements. All of which means that, once Sector gets hold of your audio loop and you have tweaked a few settings, what you can then get back is an almost infinite range of variations of that original loop. So, if you really want to squeeze the last drop of creativity out of a single loop, Sector is designed to let you do it. Beat manglers of all ages and experience levels should prepare to be impressed.

Oh, and don’t forget this is an app from Jonatan Liljedahl of Kymatica – the developer behind the excellent AudioShare and AUFX series of iOS music apps – Sector is, therefore, coming from a very well-respected stable.

Dissect Sector

So, with that context in mind, let’s summarise; Sector is, in essence, a beat slicing app for iPad that allows you to take a single audio loop, divide it into a number slices and then allows you to define just how those slices might be reassembled into a different loop by adjusting various ‘rules’ within the app that control the probability of a particular slice being chosen for playback and the probability that the slice might be ‘warped’ (processed) in some way when it is played back. And, as we are dealing with rules that define probabilities, as playback continues, you can define just how much pseudo-random variation is applied in the playback process, meaning that each time through you get variations in the performance.

You can vary the number of sectors (slices) in your loop between 2 and 32. Here a simple 4 sector option is being used.

You can vary the number of sectors (slices) in your loop between 2 and 32. Here a simple 4 sector option is being used.

So how is this all achieved? Sector’s key controls are tabbed across three main screens and you toggle between these via the Map, Seq and Wrp buttons located top-left. Visible on all three screens is the very striking visual ‘loop’ representation of your audio file that is colourfully divided into the number of sectors. The central content of the loop area changes between the three tabs.

Along the top strip and down the right side of the display are further controls that appear on all three tabbed main screens. This included the tempo setting control, access to the main menu options, the Run button which starts and stops playback of the loop and, located bottom-right, four ‘manual trigger’ buttons.

The latter can each be linked to an individual sector and, during playback, you can use these buttons to force that sector to be played back by tapping the appropriate button. This triggering isn’t instant (in the same way that, for example, hitting a note on a MIDI keyboard instantly plays that note on a synth); instead, it lines up that slice to be the next slice to be played back. Obviously, if you are using a relatively high tempo, the slice will be played pretty much instantly but, if you slow the tempo right down, you can sense more clearly how this behaviour actually works.

Also ever-present – and located mid-right – is the small summary graphic that provides a visual summary of the most recent slices played back by the app. Again, if you slow the tempo right down during playback, you can spend a bit of time working out exactly what is going on with this display. It’s pretty (although not as pretty as the main loop area) and quite useful for seeing a summary of what your various settings elsewhere within the app are doing to determine how slices get selected.

In the loop

Obviously, as Sector is a tool for manipulating audio loops, you need to get those loops into the app. The app includes both some preset audio loops to get you started and also a number of Sector ‘projects’ (that is, an audio loop plus the app settings required to mangle it). These are accessed via the Menu options. You can also open a project and replace the audio loop while retaining all the other settings.

I had no problems getting my own loops into Sector via the AudioShare route.

I had no problems getting my own loops into Sector via the AudioShare route.

Thankfully, you can also import in your own loops and this is achieved via Kymatica’s own AudioShare technology (the AudioShare app is UK£2.99 and a very useful utility to have around) or by using the ‘Open in…’ option that is present in a number of other iOS music apps. I had no problems using iTunes File Sharing to place some drum loops from my desktop computer into AudioShare and then importing those loops into Sector but, obviously, there are other routes you might take.

Sector's menu options allow you to access the presets, set the number of sectors and load or import a loop.

Sector’s menu options allow you to access the presets, set the number of sectors and load or import a loop.

Once you have your required loop within the app you can, of course, just use Sector as a standalone application. However, as the app is shipped with both Audiobus and IAA support, it is perfectly possible to integrate it into a wider music production workflow. Again, I had no obvious issues in using the app with Audiobus (it works within the Input slot) and sending the audio created on to other apps further down the Audiobus signal chain. Equally, I was able to open the app as an IAA app within Cubasis.

The only minor catch with this workflow at present is that – in this initial release at least – Sector doesn’t support MIDI clock sync. This means that you can’t sync playback in Sector to what might be going on elsewhere in the workflow other than by matching the tempo. This is not a biggie (we have been dealing with this sort of workaround under iOS since forever) but it will, of course, require you to plan accordingly.

However, developer Jonatan Liljedahl has indicated that he already has MIDI clock sync working in his current development version of the app and that feature, plus in-app recording and export, are scheduled for the first update to Sector. Both of these features will allow you to capitalise more easily on the very creative options that Sector provides.

Map work

If you load a few of the presets, the first thing that strikes you about Sector is that the central loop provides a very colourful display when in Map mode. Note that each sector is colour-coded and, if you do assign a sector to one of the lower-right manual trigger buttons mentioned earlier (tap and hold the trigger button and then tap the required sector), that trigger button will take on the same colour as the linked sector.

The central portion of the loop is dominated by equally colourful sets of arrows that provide a network of linkages between one sector and another. Sectors can be linked in this way to more than one other sector and can also be linked to themselves.

You can make links between sectors  - essentially adjusting the probability of which sector will follow another during playback.

You can make links between sectors – essentially adjusting the probability of which sector will follow another during playback.

It is this ‘map’ of linkages that, to a large extent, defines how Sector decides how to reassemble the slices of your audio loop. Each sector has a minimum of one link to another sector but it can have many links. Equally, you can also specify how strong each of these links is. Once a particular sector is chosen for playback, the choice of the next sector is determined by these links and their relative strengths (for those interested, this is a statistical concept known as a Markov Chain; where the likelihood of what occurs in the next event is entirely controlled by the single event that preceded it).

Setting and adjusting a link requires that you first select a sector (tap on it; it will become highlighted on the display) and then tapping and dragging on another sector. Equally, if you have several connections from a particular sector then you can adjust their relative strength (probability of occurring) by tapping and dragging within the central portion of the display also. A circular coloured ‘pie chart’ indicates the relative probability of each of the possible destination sectors so you can judge what you are doing.

Sector comes supplied with a small number of sample projects so you can explore the basic operation of the app.

Sector comes supplied with a small number of sample projects so you can explore the basic operation of the app.

The process of setting these links manually was the one element of the whole app that I initially found a bit mysterious. There is a bit of a knack required here but, stick with it, you will get there. First, you select a sector from which the link will go by tapping and then releasing it (it becomes highlighted). Then you need to tap on a second sector, hold your finger down and then drag away from the center of the circle. As soon as you start to move your finger in this way, an arrow linkage will appear and the strength of the link is dictated by how far you drag towards the outer edge of the loop circle.

Alternatively, you could just hit the RND button and the app will generate a whole set of random linkages from the currently selected sector. You could then adjust these to taste but it’s a brilliant way of just rolling the dice and seeing if something magical might happen.  Equally, the ALL button will link the current sector to all the others and you can adjust the strengths to the linkages to suit. Tapping the CLR button clears all the connections from the currently selected sector bar one (the connection to the next sector).

If you tap and hold any of these same buttons – RND, ALL and CLR – you get a global effect for all sectors; great if you just want to create a completely random pattern of linkages or to return to the most simple ‘every sector connected just to the next’ pattern.

The other three buttons located top-left – SH<, SH< and FLP – shift the current linkages one sector anticlockwise, clockwise or flips them in some way. Again, all these are useful tools when you just want to experiment and see what might fall into your lap.

In terms of the Map section of the app, the final piece of the jigsaw is the four ‘memory’ buttons located bottom-left. These allow you to create up to four different ‘maps’ for your loop and these are then stored when you create a preset. As you can flip between these different ‘map memories’ in real-time while Sector is playing your loop, they provide a very useful extra performance option.

Now you Seq me, now you don’t

While all these probability based options can result is an almost infinite number of loop variations on playback, a rhythm, almost by definition does require a certain amount of regular repetition in order to give it….  well, a sense of rhythm :-)

The Seq page allows you a further set of 'probability' options and, usefully, you can also force certain sectors to playback at particular steps within the sequence.

The Seq page allows you a further set of ‘probability’ options and, usefully, you can also force certain sectors to playback at particular steps within the sequence.

Thankfully, Sector has that covered via the options on the Seq page. Flipping to this page changes the central display into what is, essentially, a step-based sequencing environment. You can vary the length of the pattern between 1 and 64 steps via the step setting just beneath the circles that each represent a single step.

If you leave a step blank, the sector that plays back for that step is determined by the probability process defined in the Map page. However, if you wish, you can force the playback of a particular sector at a particular step. So, for example, if you have chosen a 16 step pattern, and one of the sectors contains a nice kick drum hit that you want to always play on the 1st and 9th steps of the pattern, then you can force Sector to do so. All you need to do is select a sector by tapping on it and then tap on any of the steps to force that sector to be played at that step in the pattern. Usefully, the step circle will fill with the same colour as the sector so you have a good visual reference to what is going on.

Sequences can be up to 64 steps in length. Smaller coloured circles indicate sectors that have a less than 100& probability of being played at that step.

Sequences can be up to 64 steps in length. Smaller coloured circles indicate sectors that have a less than 100& probability of being played at that step.

Things don’t, of course, stop there. Tapping on a circle for a second time will clear any sector from it. However, if you place a sector in a step and then drag up/down, the size of the coloured portion within the step circle changes. What you are doing here is setting the probability of that sector being trigged on that step.

So, for example, if you want to be certain that sector will play (over-riding any random/probability elements from the Map settings), then make sure the circle is fully-filled with the colour of the appropriate sector. However, if you want that sector to simply be ‘more likely’ to play at that step, shrink the size of the coloured circle; the smaller the circle, the lower the probability of that sector being triggered….  and when it is not triggered, then the sector to play back on that step will be determined my the Map probability settings.

Still with me? It might sound like this is a lot to think about but, in use, it really is very straightforward and, when combined with the more random sector selection generated elsewhere, can just help you give your new loops a sense of solidity amongst all the wonderful variability that is going on.

And there is still more….  As with the Map screen, you also get the set of six buttons top-left and four ‘pattern’ buttons located bottom-left. The latter do what you would now probably have guessed; they allow you to create four different patterns within a single Sector preset and, as with the four Map buttons, you can toggle between these different patterns during playback. Again, for performance variations, these are great.

The labels on the six top-left buttons are pretty much self-explanatory. RND simply generates a completely random set of sector selections within the current pattern. In contrast, SHF takes all the currently specified sector selections and shuffles their order. Tapping and holding on the CLR button clears the step grid completely. The final three buttons – SH<, SH< and REV – shift the current pattern one step backwards, forwards or reverse the full pattern.

This whole sequencer process is brilliantly conceived and, as mentioned earlier, allows you to ‘lock’ certain steps in the sequence to give you a solid sense of rhythm while the probability options – both here within the Seq screen and on the Map screen – mean that Sector is also able to add as much or as little ‘random’ variability each time it passes through the loop’s playback. The overall result is a huge degree of control combined with some fabulous creativity.

Warp factor

But there is still more. Flip to the Wrp (warp) page and, for each sector, you can set the probabilities for different types of audio processing to be applied whenever that sector is selected for playback. These various warp types essentially change the speed – or rather the consistency of the speed – at which the audio within the sector is played back. What results can either be ‘no effect’ (time is not warped during the playback) or a range of stutters, speed-ups, slow-downs, ping-pongs or reversing.

The Wrp screen allows you to apply various time-based effects to a sector and, again, you can configure the probability of up to four effects for each sector.

The Wrp screen allows you to apply various time-based effects to a sector and, again, you can configure the probability of up to four effects for each sector.

Setting these options is fairly straightforward. You simply select a sector to work on by tapping on it and then adjust the four sliders to set the probability of any of up to four effects being applied. To set the effect, tap on one of the effect’s graphics in the center of the loop to select it for editing and then tap on one of the 20+ effect types (9 are shown but you can scroll to see more) down the left side of the display. The arrow underneath each slider can also be used to toggle between normal or reversed playback.

There are some excellent audio effects here and, with the ability to adjust the probability of up to four possibilities (there is apparently a 5th ‘invisible’ slot that is described in the manual but I have to admit that I haven’t quite got my head around that yet), it means you have yet another means by which to add as much – or as little – random(ish) audio ear candy as you wish.

Beat this

As I mentioned earlier, Sector worked fine for me in testing within Audiobus and IAA. At this point, until MIDI clock sync is added to the feature set, either the Audiobus route (where I simply start a musical idea with Sector and record it’s output into my DAW where I can add other musical elements later) would be the most obvious workflow….  and this review took me a hour or two longer to write than it might otherwise of done because, about half way through, I managed to lose myself in combining Sector with Effectrix in Audiobus….  an awesome combination.

Oh....  this is an interesting combination :-)  Sector seems to work very solidly within the Audiobus Input slot.

Oh…. this is an interesting combination :-) Sector seems to work very solidly within the Audiobus Input slot.

However, even used as a standalone app with audio loops imported via AudioShare, it doesn’t take a very long to see the potential of Sector. This is one heck of an app and, if you like to create your own beats – and if you really want to wring the life out of even the most jaded of drum loops – this is a very modest price to pay to be able to do it.

Once you have got your head around the core options, I also should emphasise that the interface is an absolute joy to use. The engine and/or mechanics of what the app does with all this probability magic is very clever indeed but the way you access all these options through the interface is brilliantly executed.

What next?

Jonatan has already declared that the ability to sync to MIDI clock is on the way along with recording and export options. These will all be very welcome. However, having enjoyed using Sector so much, I couldn’t help but let my mind wander into what else it would be great to see and there were a few (mostly minor) possibilities that sprang to mind.

Sector also includes some supplied audio loops....  but this is where you can also access and loops of your own that have been imported into the app.

Sector also includes some supplied audio loops…. but this is where you can also access and loops of your own that have been imported into the app.

First, given that the interface already includes the Map buttons (on the Map screen), the Seq buttons (on the Seq screen) and the manual trigger buttons (that appear on all screens), Sector has a lot of options for triggering pattern changes on the fly. As such, once you had created a preset based around a particular loop, it is easy to imagine using the app in a live performance context. However, to make that really easy, it would be great if all of those buttons – Map, Seq and manual trigger – could be available on a single display rather than having to toggle between the Map and Seq displays. Perhaps an additional ‘live performance’ screen might be a possibility in a future update. Equally, being able to link these buttons to an external MIDI controller would be great.

Second, I think users might find it really helpful if there was a simple way to audition an individual sector while the loop was not running (if there already is, then I’ve obviously missed it). This way, you could more easily identify which sectors you might want to use as the ‘core’ of your loop and give the highest probability of playback to or add to key steps in your sequence. You can, of course, simply listen to the loop (perhaps even having slowed the tempo down) to identify this….  but the ability to tap on a sector and just hear it in isolation would be useful.

Finally, it is worth noting that when you adjust the master tempo setting in Sector, the app’s audio engine adjusts the loops playback speed to match so everything stays in time. However, this also results in a change in pitch with everything going down in pitch for slower tempos or up in pitch for higher tempos.

This is, of course, how tempo-matching used to work in days of old, both in samplers and on the desktop and, in the context of an app like Sector, it is not such a massive deal as you are generally using the app to create electronic or off-the-wall rhythmic effects anyway. However, if the app did include an option whereby the tempo-matching could be done either with, or without, pitch shifting (as can be done in lots of audio processing tools in the desktop environment), this would also be a brilliant option. Indeed, the ability to tempo-match an audio loop while retaining its original pitch is something that is missing from many (although not all) iOS DAWs. It would be great if Sector could offer that function to users as a bit of a bonus :-)

In summary

There are lots of iOS music apps that ‘do rhythm’ and there are a number of brilliant effects apps that can take a rhythmic loops and mash it in various ways. However, I don’t think we have yet seen anything quite like Sector. Yes, it perhaps has a little bit of an overlap with something like Steinberg’s LoopMash which also slices audio loops and uses a probability-based process to reassemble those slices, but in all other respects, the two apps are very different in approach.

You can vary the number of sectors used between 2 and 32 via the Menu options.

You can vary the number of sectors used between 2 and 32 via the Menu options.

However, good though LoopMash is (and, on the desktop, where unlike the iOS version, you can load your own loops into it, it is very good indeed), in terms of the transparency of the interface and the degree of control it offers, Sector currently wins hands down. For creating something that is constantly new from something old – really recycling your audio loops – this is just a fabulous tool.

Indeed, Sector is so good that, rather like Stereo Designer (which I reviewed last week), I really do wish it was available as a VST/AU plug-in so I could use it on my desktop system. I think we are starting to see a number of iOS music apps appear where it is possible to make that case; that, in their class, they are actually as good as, or even better, than what’s available on the desktop. If Sector was available as a desktop plug-in I, for one, would gladly put it to use alongside the best of my other beat slicing tools.

But, of course, it is currently iOS only….  and it is utterly brilliant. Support for MIDI clock will be great to see but, even as a standalone app, if you like to slice and rearrange your drum beats, Sector is a top-notch tool. And, as of the time of writing, it is currently available at a special introductory price of UK£4.99, if you are going to get it, then now’s the time to hit the download button.

Sector is brilliant software regardless of the platform and ridiculously cheap considering what it can do…..

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    Comments

    1. Michael Cluff says:

      Yes, I second the motion to be able to preview a sector. Great app either way!

    2. Great review and actually a good tutorial for me as I haven’t had chance to play properly yet, thank you, +1 for previews too!

      Importing REX files would be lovely or some other slice marker tool. I’m still unclear how loops are actually ‘sectored’ but I guess this will become clear once I start using it?

      • Hi Baddcr… thanks for the kind words – always appreciated :-) I’ve no idea how the original ‘sectoring’ is done but I suspect it must include something a bit more intelligent that just dividing the loop into sub-sections of equal length…. possible hunting for transients? Maybe Jonatan will pop by and let us know? :-)

    3. An in app editor would be cool, but maybe that isn’t really the point.

      In any case, I would like to see a soft attack option and a fade out in each sector so that pads, and maybe then less percussive material, like synth pads/loops would not glitch (the bad kind) so frequently. It is a brilliant piece of work, but I also believe one that will demand a lot of concentrated experimentation to get it into your work flow in a musical way, and it will absolutely challenge your ideas of what a musical instrument/tool is…Throw your expectations out the window, as this is the new poster child benchmark for convention defying app.

      Bonus Marks to Jonatan Liljedahl for the sheer visual beauty of all of his apps. It means something to me to get knocked out by an interface…I look forward to returning to the environment.

      • Hi Chris… agreed; this is a brilliant tool that, at one level, is very easy to use but, at another, is also very deep. I know Jonatan has lots of ideas about how to take the app onwards. Let’s hope he gets the support required to do just that…. Best wishes, John

    4. awesome app! got it yesterday and highly recommend it to all!
      good job Jonahan!

    5. Thanks for taking the time to make this informative review. That looks like a difficult app to explain. You did an excellent job. It helped me a lot.

      • Hi Jerry, thanks for the kind words… always appreciated… and also glad if you think the piece helped as that’s always the intention :-) Best wishes, John

    6. Just won this through your giveaway. Can’t wait to fire it up this evening! Thanks all!

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