Разработчик приложения SpectrumGen: Alexander Zolotov
SpectrumGen is a spectral synthesizer with simple and effective user interface. It is a bit like the PixelWave experimental synth, but now you can draw the spectrum of sound!
Key features:
• multitouch arpeggiator;
• recording;
• export to WAV (via iTunes File Sharing);
• copy to share with another iOS sound apps;
• eight predefined timbres;
• changeable number of octaves (from 2 to 8);
• it is possible to draw the spectrum and play it at the same time;
• MIDI IN support.
Dark colors - low frequencies (bass). Bright colors - high frequencies.
Video: http://goo.gl/LcMec
Also if you want to draw a waveform directly, check my another app - PixelWave.