LMMS - Make music with a free, cross-platform tool
KORG Gadget - KORG Gadget - From iOS to Mac. Music production software to help your musical imagination become reality.
Reaper - Reaper is a focused digital audio workstation (DAW) developed by Cockos. In the creation of the software, the digital audio technology company intended to make audio editing accessible to the masses.
Poison-202 - Vintage MIDI synthesizer for Mac and iOS
Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
KORG iMS-20 - KORG iMS-20: Transform your iPad into a complete analog synth studio!