iOS Musician Apps (132) Supported Technologies is Inter-App Audio (IAA), Instrument Type is Synth

PixiTracker 1BIT is a simple and fun tool to quickly create musical sketches, chiptunes and experiments with TRUE 1-BIT SOUND (like on old microcomputers).
No musical knowledge required.

Pixound provides a deep musical experience that lets you instantly create music using any picture.

SpectrumGen is a spectral synthesizer with a simple and effective user interface.

The unique dynamic wavetable synthesis allows you to explore an unprecedented wide range of sonic territory.

PixelWave is an experimental synth with old school pixel interface.

Shape is a polyphonic synthesiser allowing the user to draw the shape of the oscillator waveform.

GarageBand is a DAW by Apple.

AutoArp turns your iPhone (or iPod Touch) into a musical instrument that is halfway between a traditional auto-harp zither and an arpeggiated analogue-style synth.

TweakyBeat is a drum machine synth.

SunVox is a small and fast cross-platform modular synthesizer with pattern based sequencer (tracker).

Droneo is a synthesizer which drones with various timbres and precise intonations that blur the distinction between tones, timbres and chords. Its drone is great for meditation, centering, and calming,  walking and biking, but also can be set up for discordant noise and insect-like buzzing and chirping.