microSynth is a standalone software synthesizer with multi track sequencing capability. It uses your Mac's keyboard as an input device, so you can play and compose music without connecting any outboards. "microSynth" uses "QuickTime Music Synthesizer" as its sound source by default, but also has a capability to load "SoundFont2" and "DLS" files.
What's new in microSynth
Version 1.1.6: Release notes were unavailable when this listing was updated.