Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
VCV Rack - A cross-platform modular synthesizer.
nlog Synth - Professional Virtual Analogue Synthesizer ::: check nlogmusic at YouTube :::
miRack - Eurorack-style modular synthesizer for iOS.
cassini - Polyphonic Synthesizer for iPhone/iPod touch
SynthEdit - Visual programming software to build your own synthesizer.