|AHX Tracker on Amiga|
Tracker music software uses the 'other' keyboard when creating music. Using a vertically scrolling window of notes and hex numbers instead of the more traditional piano roll makes the process much more scientific. The trackers first appeared in early Commodore computers and took advantage of samples and the limited CPUs and user interfaces of that time. Since trackers make very good use of limited CPUs, the iPad is a good candidate for theses types of DAWs despite the limited keyboard.
My first exposure to trackers was the excellent Sunvox app on the iPad which also has many other versions for almost any computer or cell phone out there. I downloaded the free version for my iMac as well and use that for final mix down and mastering.
I think this gave me a bit of a skewed view on trackers since SunVox is in many ways unique among trackers. Rather than relying primarily (or solely) on samples, SunVox includes a very flexible and powerful modular synthesizer. It is optimized for light CPU usage so some of the sounds reflect that but you have an extremely rich set of building blocks to craft your own sounds with it.
I was simultaneously enamored of the concept and confused by the interface which is odd - typical of cross-platform tools. While I tried to figure SunVox out, I took a look at another option on the iPad called iSequence by BeepStreet.
BeepStreet took the traditional tracker concepts and built an interface ideal for touch screens and the iPad in particular. The iSequence "tracking" occurs atypically left to right on the iPad which better suits the landscape screen. Also, more like older trackers, iSequence depends on samples and offers hundreds free and still more available as in app purchases - most at $2 per pack - pretty reasonable overall. The program also lets you bring in your own loops and samples, so it is very flexible.
I eventually gave SunVox more of a try and created a few nice tracks with it. In terms of sheer power, it has it and seems to be updating new features every month. I think this is the most fun tracker I own. While it is not a perfect fit on the iPad interface, it is very nice to be able to move my work back and forth between the iPad and iMac. This is the only tool I own that makes that so simple to do. Garageband is a one way trip "up" and NanoStudio is a bit flaky with their desktop versions.
I have gotten so used to the trackers on the iPad that I am evaluating another sort of "hybrid" tracker that is extremely powerful on the desktop called Renoise. Renoise is much closer to the traditional trackers in its look and feel but also allows for effects processing and supports VSTs and AU plugins - so while it also uses samples quite a bit, there is a great way to incorporate soft synths in it. Renoise is not free but is reasonable for a desktop DAW at $78. I am still on the test drive version but may spring for it at some point. Might be a great addition when I don't want to use Logic 9.