Play/Stop: Use the main Play button.
Toggle Step: Click or drag on the grid to add/remove notes.
Save/Load: Use Save/Load buttons to handle MIDI files.
Step Options: Double-click a step for Velocity, Ratchet & Probability.
Track FX: Click the 'Opt' button for Pitch, Attack, Release, and other effects. Release controls Choke falloff.
Clear Sample: In the FX popup, clear a loaded sample.
Rename Track: Double-click a track name to rename it.
MIDI Record: Arm 'Record', then play notes on your controller.
Click anywhere to start.