iOS Musician Apps (117) Supported Technologies is Inter-App Audio (IAA), Instrument Type is Synth

Laplace is a physical-modeling synthesizer based on resonator synthesis that makes it easy to create bowed string, plucked string, blown pipe and metallic sounds.

Jam Synth is a fully featured monophonic guitar synthesizer / multi FX for iOS.

Multilevel Interactive Sound Synthesizer. Up to 240 Frequency Modulation Oscillators or simple Wavetable Additive.

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.

iPhilicorda is an emulation of a vintage organ from the sixties, the Philicorda, created by the Dutch company Philips.

AudioKit Synth One is a completely free & open-source professional iOS Synthesizer. 

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

SoundScaper is an experimental sound mini lab for creating unusual soundscapes, atmospheric textures, drones, glitches and noises based on circuit bending principles.

Moebius Lab is a multimorphic sound processor which contains a synth, a varispeed stereo sample player, effects and LFOs that can modulate each parameter.

Pure Acid is a bassline synthesizer and drum machine in one app.

Hexaglyphics is a 13-bit noise generator with an interface based on an original alphabet for hexadecimal values.

The Moog Model 15 App is the Moog modular synthesizer and synthesis educational tool.

TweakyBeat is a drum machine synth.

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

Groove Rider GR-16 is a professional step-sequenced groove box, inspired by professional hardware drum machines and rhythm boxes.

miRack is a Eurorack-style modular synthesizer. It aims to provide user experience and audio quality close to those of the real Eurorack hardware.

Xynthesizr is a streamlined yet capable 32-step matrix sequencer/monotimbral synthesizer with generative features and MIDI.

Lagrange synthesizer has two oscillators, a noise generator and two filters that can be selected from various algorithmic models.

PixelWave is an experimental synth with old school pixel interface.