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

This fully featured monophonic synthesizer can create a huge variety of sounds. Fat basses, stabby leads, glitchy noises, old style chip tune sounds (including arpeggios), weird percussion, you name it.

With EGSY01 you can create sounds, from modern ones to vintage analog ones, working with arpeggiator, step sequencer and FM, addictive and subtractive synthesis.

Turning your iPad in to a classic sounding theremin.

DRUMLAB brings a new approach to the Drum Machine by allowing you to play with both Samples & Synthesis drum sounds.

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.

DRC is a virtual analog polyphonic synthesizer that recreates the characteristic sound of an analog synthesizer.

Dazibao is a polyphonic synthesizer programmed by an innovative interface : you create several tones, then you arrange them on several time lines.

This app reproduces the functionality of Casio’s best-selling CZ-series models, such as the CZ-101 (first released in 1984), and also includes new functions.

Cyclop is a monophonic synthesizer. It does one thing very well: delivering cutting-edge digital madness at the low end of the frequency spectrum.

Cube Synth is a groundbreaking new software instrument giving you the power and flexibility of additive synthesis together with easy editing and morphing capabilities.

Continua is a three-oscillator / dual-filter six-voice virtual analog synth, with fully polyphonic modulation sources and built-in custom-designed effects, for everything from complex, evolving chill-out soundscapes to New Wave synth stabs.

CHAiOS SYNTH 2 is a synthesizer/melody generator that creates unique melodies with just one tap.

Fed up with standardized presets and instruments? Feel lost in overcomplex filters and effects? Don’t wanna sound like everyone else? BLEASS is just the right instrument for you: it unleashes your inner musical creativity by bringing music production and performance to its very core: play, perform, compose beats and melodies in a new yet intuitive way thanks to its multitrack sequencer, synthesizer and drum machine.

bent.fm is a full FM model of a circuit-bent synthesizer.

Baervaag brings FM synthesis to the masses! An easy to use but still tweakable synthesizer, accessible to everyone.

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.

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

Epic 64-voice Virtual Analog / PCM iPad Synth. Inspired by the Digital Synths of the 80s and 90s.