There's no doubt that iOS music making has come on leaps and bounds in the past year or so.
While, given their nature, Apple's mobile devices still can't compete directly with Macs and PCs in music making terms, they've certainly become viable platforms for producers and musicians to work with. This is especially true now that we have Audiobus and Apple's own Inter-App Audio, which enable compatible apps to be routed into and through one another. The iPad in particular has become a viable tool for sketching ideas, making basic recordings and working on tracks.
But just as with any production platform, if you want to piece a track together, you're going to need a DAW-like application to act as your 'hub'. Here are some of our favourite options - listed in no particular order - starting with the big one