GarageBand

Music Production
Transport
SPACE Play / Stop mac
R Start recording mac
Go to beginning mac
C Toggle cycle (loop) region mac
Tracks & Regions
S Solo selected track mac
M Mute selected track mac
+T Split region at playhead mac
+J Join selected regions mac
DEL Delete selected region mac
+D Duplicate selected region mac
Editors & Windows
E Open / close editor (Piano Roll or Audio Editor) mac
+I Show / hide Track Info mac
+R Show / hide track header controls mac
General
+Z Undo mac
+⇧ Shift+Z Redo mac
+S Save project mac
+A Select all mac