RP-1 review – Kai Aras supplies a new delay app with Audiobus, IAA, AU and Link all included

Download from iTunes App StoreRP-1 logo 1I did a couple of audio effects/processor app rounds articles a while ago here on the Music App Blog. It is a category that we have some excellent offerings within whether you are looking for more conventional processing options or more creative ‘out there’ effects. However, given the budget pricing of many iOS music apps, and given the fact that, until the AU format becomes more widely adopted, you are limited to a single instance of each music app running at any one time, there is certainly no harm in have multiple options for more commonly used effects/processing such as EQ, compression, reverb or delay.

In the last of these categories we now have a new option; RP-1 from Numerical Audio and developer Kai Aras. RP-1 is a universal app, requires iOS9.0 or later, is a 19MB download and is priced at just UK£4.49/US$5.99. I’ll get into the details of the effects options in a minute but it is also worth noting that, on the technical print, RP-1 is bang up to date. As well as getting Audiobus and IAA support, therefore, the app also launches with both Ableton Link (tempo sync your delays via Link) and Audio Units (AU) support. The latter means that you can, of course, run multiple instances of the app within a suitable AU host. I had no problems doing this via either Cubasis or AUM.

RP-1  - a very flexible delay effect with Audiobus, IAA and AU support.

RP-1 – a very flexible delay effect with Audiobus, IAA and AU support.

There will be a long delay

RP-1 is, in fact, two stereo delays in one. The main (the documentation refers to this as a ‘long’ delay) Delay section does exactly what you would expect; it allows you to add a range of different ‘echo’ treatments to your audio.

As can be seen in the various screenshots, you can either set a time for the delay or ‘sync’ it to the tempo of whatever host you happen to be running within (for example, via IAA sync or Ableton Link). If tempo-sync’ed, then the large Time control shows beat divisions for setting the repeat times… and you also get three buttons for toggling between straight beats, dotted or triplet feels.

RP-1 also supports Ableton Link for sync'ing your delay timings to other apps.

RP-1 also supports Ableton Link for sync’ing your delay timings to other apps.

As well as the fairly conventional Feedback control) for adjusting just how many repeats you get) and Mix control (for adjusting the wet/dry balance), you also get low pass and high pass EQ controls (so you can focus the tonal properties of the delays) and the rather wonderful Spread control. The latter spreads the delays more obviously into the left/right of your stereo image and is quite addictive :-)

You also get a Bypass button and the rather unusual Loop button. This is almost like an internal recorder feature as the delays seem to be stacked on top of one another on a bar-by-bar basis as you hold the button down. The normal delay processing returns once you release the button.

All mod cons

The second stereo delay line exists in the Mod section and this generates a range of short delay options to create various modulation-style effects such as chorus and flanger. This section is pretty simple control wise. You get a Mod type dial (chorus, flanger and vibrato are the options available), a Mod % (amount) and Mod Frequency control; just dial in what you want and away you go.

The app worked very smoothly via AU...  as seen here within AUM.

The app worked very smoothly via AU… as seen here within AUM.

Again, you also get a bypass button but, interestingly, you can place the Mod section either pre- the Main Delay section or post- it. The results are, of course, somewhat different in each case. And, if you want to explore that, then simply open up the Preset list (located top right) as the factory presets includes some very useful examples where the Mod section is placed both pre- and post- the Delay.

When used via IAA or Audiobus, the main display also includes both input and output meters with level controls. This section also includes Mono and Mute buttons for the input and output respectively.

Techie talk

As I mentioned above, I had no problems using RP-1 via AU in both Cubasis and AUM. Eually, the app seemed very happy when used via IAA (again, in both Cubasis and AUM) or via Audiobus. The user interface is, obviously, somewhat different depending upon which format of the app you are using; you don’t get the input/output sections when used via AU.

The app ships with a number of presets to get you started.....

The app ships with a number of useful presets to get you started…..

The only other technical point worth noting is that the preset system seems to operate slightly differently between the IAA/Audiobus and AU formats. Under AU, even if your host supports presets (as AUM does), then I didn’t see the Factory presets that are available via IAA/Audiobus (NOTE: this bug was suitably squashed in the v.1.0.5 update). I could, however, create my own presets within AU or IAA…. but a preset created in one format didn’t seem to then appear in the other. I’m sure this is a limitation of the current AU spec rather than a shortcoming in RP-1. Hopefully, iOS10, when it eventually appears later in the year, will bring us some refinements to the AU format.

Repeat after me

What about the sound of RP-1? Well, on that front, I don’t think many will have much to complain about. The app manages to combine a pretty straightforward control set (no learning curve) with a surprisingly wide range of treatment possibilities. Combining the ‘long’ and ‘short’ delay sections allows things to get quite creative and, if you opt for a triplet feel to your main delays, then you can get… well… quite trippy.

The full control set provides yo with both conventional and creative delay options.

The full control set provides yo with both conventional and creative delay options.

However, even as just a conventional delay – without the Mod section – RP-1 does a very good job. It sounded great when used as an insert or send effect on conventional sources such as vocals but, equally, could also be used to spice up a simple drum or percussion loop or to add some character to a simple synth lead line.

I particularly liked the way you could clean out the low end and high end of the delays via the EQ controls. This allows you to have an obvious set of repeats present but without the sound filling the mix with too much clutter… and rolling off some of the highs does give the sound a more ‘analog tape delay’ sound. Equally, that Spread control is very effective if you are looking to give a sound a greater sense of stereo.

The preset system also function when the app is used via AU within AUM.

Thanks to the v.1.0.5. update to the app, the preset system also functions when the app is used via AU….  as shown here within AUM.

In summary

There is little not to like about RP-1. It performed pretty much flawlessly for me on my iPad Pro/iOS9.3 test system and it is bang up to date in technical terms. The effects options provided can go from conventional delays though to some rather nice trippy repeats and, while there are more obviously ‘creative’ effects apps out there (think apeDelay, Flux, DFX, VanDelay or Turnado, for example) that offer delay, thought of as a ‘conventional delay plus’, RP-1 is very good indeed.

And, at just UK£4.49/US$5.99, it really is set at a pocket money price. No matter how long I spend with my iOS music app collection, I’m still regularly surprised at just what fabulous value for money we get. RP-1 is yet another example of that; no fuss to use, sounds great and very affordable. RP-1 comes highly recommended.



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