Keyboard commands

EnterToggle Play mode
SpaceToggle Record mode
Arrow KeysNavigate through pattern
A-ZPlayback notes (Set you keyboard layout in Options)
F1 -> F6Select Octave 1 -> 6
Page up/Page downNavigate up/down 16 rows (1/4th of the pattern length)
HomeNavigate to top of pattern
EndNavigate to bottom of pattern
TabNavigate to next track
-Select previous sample
+Select next sample
Numeric Keypad 0-9Select Sample 1-10

In recording mode
A-ZEnter notes (in the note column)
0-9Enter effects (in the effect column)
\Note-Off (in XM-mode)
DelClear note
BackspaceClear note
Shift+EnterInsert note (shift notes down)
Shift+backspaceRemove note (shift notes up)

Selection*
Shift+Arrow KeysMake pattern selection
Shift+ASelect entire track
Shift+CCopy selection
Shift+XClear selection (and copy it)
Shift+VPaste selection
EscClear selection
* A selection can span multiple tracks.
Instead of Shift you can also use Ctrl, Alt or Command.

In general
Ctrl-ZUndo
Ctrl-YRedo
EnterConfirm / OK / Play
EscCancel