csSpectral is a real-time, Csound-based, multi-effects processor featuring a Streaming Phase Vocoder and six other FFT-based spectral algorithms. The diverse collection of real-time DSP effects let you create unique textures and timbres by transforming your voice, instrument, or iTunes library.
csSpectral also supports Audiobus, allowing you to send and receive audio from other apps, making the processing possibilities nearly endless.
csSpectral is available for $19.99