The often expensive Aurora Sound Studio HD is less so today, with a sale bringing it down to $20! An excellent deal for those of you that like step-sequencer apps.
This Tenori-style tone matrix Studio has up to 14 instrument tracks. Each of these can be loaded up with one of four instruments: Drum Machine, Analog Synth, Pad Synth, and Sampler.
Rounding out the package is a whole bunch of effects and a sleek looking mixer.
Here's a demo song from Diabolic Diabetic on SoundCloud: