Green Oak Crystal is available now for iPad, iPhone and iPod Touch. For years Crystal is one of the best free desktop synthesizers. The mobile version is not expensive too, it costs only $0,99 (€0,75).
The synthesizer offers different synthesis techniques: subtractive, granular, wave sequencing and frequency modulation (FM). It has lots of effects and modulation options. Crystal is playable on the mobile devices with the added 1 octave keypad.
Green Oak will soon release the more advanced Crystal XT against a premium price. XT offers the exchange of patches with the desktop version of Crystal and adds midi keyboard input via the iPad’s camera adapter. Midi keyboard input support is added by Apple from OS 4.2.
This video demonstrates the mobile version of Crystal:
The first tutorial: