[iPhone God App] It was found using the CASSINI Synth for iPhone actually

Highly Tweakable Polyphonic Synthesizer for iPhone/iPod touch
3 OSCs + 2 Filters + AMP + 9 EGs + 6 LFOs + 3band EQ + Saturator + 2 Delays + Arpeggiator

* Inter-App Audio support (v1.3.0)
You can stream live audio directly to other InterApp-Audio compatible apps directly.

* Audiobus support
Now you can stream live audio directly to other Audiobus-compatible apps! See http://audiob.us for more information. (including. state saving in Audiobus2)

* 3 Oscillators + 1 Sub-Osc
- Sawtooth, Pulse(PWM), Triangle, Sine, Noise, FM, 8bitOsc
- Waveshape Modulation
- Oscillator Sync
- Ring Modulation

* 2 Filters
- LP24, LP18, LP12, LP6, BP, HP, Formant

* AMP
- Overdrive
- 3 Band EQ
- Auto Pan

* 9 Envelope Generators
- DAHDSR (Delay, Attack, Hold, Decay, Sustain, Release)
- Velocity, Keyboard Tracking

* 6 LFOs
- Sawtooth, Pulse, Triangle, Random, 16 Step Sequence
- Waveshape Modulation
- Envelope for LFO (AD/AR)

* Modulation Delay
- Delay Time: 1-2000ms / Tempo Sync
- Delay Time Modulation

* Filtered Stereo Delay
- Resonant Filter (LP, BP, HP)
- Filter Modulation

* Programable Polyphonic Arpeggiator
* Scale/Chord Remapper
* Support for CoreMIDI device (input)
* Virtual MIDI-IN & Background Audio
* Scrollable keyboard (Horizontal scrolling at the bottom edge of the keyboard)

* Recorder
- Audio Copy (Compatible with INTUA BeatMaker, Apple GarageBand and so on.)
- Export wav file via iTunes File Sharing
- The recording time is limited to 3 minutes.

Further information at http://ios.icegear.net/cassini_iphone/