Regular iOS music makers will be familiar with AppBC as the developer behind Studiomux and Modstep apps. The latter includes some of the Studiomux technology but also offers a fully-blown MIDI sequencer with both step sequencing and piano roll editing environments. If your music making revolves around MIDI, rather than audio recording, then Modstep is a powerful option for sequencing on your iPad.
I did a full review of Modstep just after it was launched and the feature set is impressive. You can use unlimited MIDI tracks and there is support for multiple MIDI continuous controllers on each MIDI track so you can modulate your sound sources to keep your sounds changing, etc. The first significant update added Audio Units (AU) support which was great to see.
I have to say that Modstep has rapidly evolved into a very powerful MIDI music creation environment and each update simply adds to the already impressive functionality. It is perhaps not for the faint-hearted as that power comes with a depth that does involve an initial learning curve but, as a stand-alone MIDI sequencer, it’s clip-based approach is both very flexible and very creative.
Anyway, if you have not yet given the app a try, then now might be a good opportunity. In what I think is a limited-time offer, the app is currently on sale and 50% off it’s usual pricing. The app requires iOS8 or later if you want to use the audio and MIDI streaming to PC/OSX provided by the Studiomux technology but, as a stand-alone (iOS only) app, will work with iOS5.1.1. It requires an iPad, is a 53 MB download and is usually priced at UK£14.99/US$19.99. At just UK£7.77/US$9.99 while on sale, this is a real bargain for those wanting a comprehensive MIDI-only sequencing environment. Be quick though as I’m not sure how long the sale price will hold.