Modern music making can offer infinite options, but if a quick, simple, no-nonsense drum, bass or synth pattern is what you need, check out the free Auxy sequencing app.
The minimal interface puts the emphasis on speedy and easy creation of melodies and chords, which play through Auxy's onboard sound generators. Users are locked into a scale, so it's pretty hard to put a foot wrong.
Free it may be, and simple certainly, but we can see there must be more in the pipeline for Auxy. Currently, your pattern can be exported (via DropBox or sent direct to SoundCloud), but you can't save your constructions.
To us, this hints towards a future release of a new, paid version, or the addition of in-app purchases. Features such as MIDI output would be worth paying for to an audience hooked on the free version.
Keep up to date on the Auxy website, and get the app on the App Store via your iPad....