In general these keyboard shortcuts can be used in combination with each other. For example, you can simultaneously hold down the Command Key to select a different tool, and the Shift Key to toggle the setting of Cursor Snaps to Grid.
Space Bar: Toggles Pause. (Begins playback if not paused)
ESC: Stop
‘ or ~: Toggle Record
Return: Rewind
Enter: Rewind and begin playing
Delete: Same as choosing “Clear” from the edit menu
Up-Arrow: Previous Take
Down-Arrow: Next Take
Left-Arrow: Previous Player
Right-Arrow: Next Player
Numbers 1-9, and 0: Selects the current Player’s Takes 1-10
Shift: Toggles “Cursor snaps to grid” for dragging operations. (Stretch notes, move notes, paint notes, box select etc.). Extends selection for box-selection, or when selecting in lists.