Undo

`⌘ Cmd` + `Z`

All hotkeys for Apple GarageBand

General Start or stop playback	`Space`
General Go to beginning	`⤶ Enter`
General Go to end of last region	`⌥ Option` + `⤶ Enter`
General Move forward	`.`
General Move back	`,`
General Move cycle area forward	`↑ Shift` + `⌘ Cmd` + `.`
General Move cycle area back	`↑ Shift` + `⌘ Cmd` + `,`
General Move forward by visible width of the timeline	`End`
General Move back by visible width of the timeline	`Home`
General Turn Catch mode on/off	`<`
General Zoom out	`⌘ Cmd` + `←`
General Zoom in	`⌘ Cmd` + `→`
General Create a new track	`⌥ Option` + `⌘ Cmd` + `N`
General Create a new audio track	`⌥ Option` + `⌘ Cmd` + `A`
General Create a new software instrument track	`⌥ Option` + `⌘ Cmd` + `S`
General Duplicate the selected track	`⌘ Cmd` + `D`
General Delete the selected track	`⌘ Cmd` + `Del`
General Rename the selected track	`↑ Shift` + `⤶ Enter`
General Arrow Select the previous staff event	`↑`
General Select the next staff event	`↓`
General Mute/Unmute the selected track	`M`
General Solo/Unsolo the selected track	`S`
General Turn monitoring for the selected track on/off	`Control` + `I`
General Show/Hide automation for the selected track	`A`
General Delete all automation on the selected track	`Control` + `↑ Shift` + `⌘ Cmd` + `Del`
General Unmute all tracks	`Control` + `⌥ Option` + `⌘ Cmd` + `M`
General Unsolo all tracks	`Control` + `⌥ Option` + `⌘ Cmd` + `S`
General Undo	`⌘ Cmd` + `Z`
General Redo	`↑ Shift` + `⌘ Cmd` + `Z`
General Cut	`⌘ Cmd` + `X`
General Cut an arrangement marker together with its regions	`⌥ Option` + `⌘ Cmd` + `Del`
General Copy	`⌘ Cmd` + `C`
General Paste	`⌘ Cmd` + `V`
General Delete	`Del`
General Select all	`⌘ Cmd` + `A`
General Select the previous score event	`←`
General Select the next score event	`→`
General Split selected region or event at the playhead	`⌘ Cmd` + `T`
General Join selected regions or notes	`⌘ Cmd` + `J`
General Loop selected region continuously	`L`
General Add selected region to the Apple Loops Library	`Control` + `↑ Shift` + `O`
General Rename the selected region	`↑ Shift` + `N`
General Turn Snap to Grid on/off	`⌘ Cmd` + `G`
General Show/Hide alignment guides	`⌥ Option` + `⌘ Cmd` + `G`
General Start recording	`R`
General Turn the Record Enable button for the selected track on/off	`Control` + `R`
General Turn the cycle area on/off	`C`
General Turn the metronome on/off	`K`
General Turn count-in on/off	`↑ Shift` + `K`
General Transpose selected notes up one semitone	`⌥ Option` + `↑`
General Transpose selected notes down one semitone	`⌥ Option` + `↓`
General Transpose selected notes up one octave	`⌥ Option` + `↑ Shift` + `↑`
General Transpose selected notes down one octave	`⌥ Option` + `↑ Shift` + `↓`
General Print score notation	`⌘ Cmd` + `P`
General Show/Hide the Musical Typing window	`⌘ Cmd` + `K`
General Show/Hide Smart Controls	`B`
General Show/Hide the Score Editor	`N`
General Show/Hide the Piano Roll Editor	`P`
General Show/Hide the Loop Browser	`O`
General Show/Hide the Library	`Y`
General Show/Hide the Editor	`E`
General Show/Hide the Note Pad	`⌥ Option` + `⌘ Cmd` + `P`
General Show/Hide the Media Browser	`F`
General Show/Hide the Arrangement track	`↑ Shift` + `⌘ Cmd` + `A`
General Show/Hide the Movie track	`↑ Shift` + `⌘ Cmd` + `O`
General Show/Hide the Transposition track	`↑ Shift` + `⌘ Cmd` + `X`
General Show/Hide the Tempo track	`↑ Shift` + `⌘ Cmd` + `T`
General Show/Hide the master track	`↑ Shift` + `⌘ Cmd` + `M`
General Open a Movie	`⌥ Option` + `⌘ Cmd` + `O`
General Create a new project	`⌘ Cmd` + `N`
General Open an existing project	`⌘ Cmd` + `O`
General Close the current window or project	`⌘ Cmd` + `W`
General Minimize the GarageBand window	`⌘ Cmd` + `M`
General Save the current project	`⌘ Cmd` + `S`
General Save As	`↑ Shift` + `⌘ Cmd` + `S`
General Show GarageBand preferences	`⌘ Cmd` + `,`
General Hide GarageBand	`⌘ Cmd` + `H`
General Quit GarageBand	`⌘ Cmd` + `Q`
General Open detailed Help (move the pointer over an interface item)	`⌘ Cmd` + `/`