Overdub software instrument recordings
Overdubbing is the process of recording a performance on top of an existing performance, merging them into a single region. You can use this process to add a supplementary recorded sound to a previously recorded performance, for example.
During recording, any adjustments to knobs or other controls in the Smart Controls area are recorded as region-based automation. You can use MIDI Draw to edit the Smart Controls Recording later.
Overdub a software instrument recording
Choose GarageBand > Preferences.
In General preferences, choose Merge from the “Cycle on” pop-up menu
Drag left or right in the top part of the ruler.
The cycle area appears as a yellow strip in the ruler, and Cycle mode is automatically turned on.
Click the Record button in the control bar (or press R) to start recording.
Recording begins after the predefined count-in.
Use your MIDI keyboard, Musical Typing window, or onscreen music keyboard to play some notes. Record as many cycle passes as you wish.
Click the Stop button in the control bar (or press the Space bar) to stop recording.
The end result is a single MIDI region that contains the merged performances from each cycle pass.