iOS Musician Apps (32) Instrument Sounds is All-in-one

Load any MIDI file and sound library (a small General MIDI sound font is included). Play midi files with additional features.

Caustic 3 is a music creation tool inspired by rack-mount synthesizer/sampler rigs.

Synthecaster fuses elements from guitars and keyboards into a full range polyphonic instrument that is intuitive, accommodates a wide variety of playing styles, and generates an even wider variety of sounds.

Thesys is a MIDI stepsequencer app, giving you control over just about all aspects of your favorite MIDI devices.

Anyone can create pro-quality music in minutes with the world's only chord-based audio loop app.

No time to delve into the big and serious music apps? PixiTracker is what you need! It is a simple and fun tool to quickly create musical sketches, chiptunes and sound experiments.

GarageBand is a DAW by Apple.

Chordbot is a songwriting tool / electronic backup band that lets you create and play complex chord progressions in different arrangements easily. Just add some chords, select a comping style and hit play.

Even if you've only played air guitar, ThumbJam lets you sound like a pro.  Pick an instrument and jam - with all the scales to choose from you'll never hit a wrong note.