Select the vocal track you want to chop up in GarageBand by clicking on its name.
Double-click the vocal track to view it in the Track Editor for a closer look.
Click the playhead cursor at the top of the screen, which indicates where the song will start playback, and move it to the section of the vocal track you want to chop.
Press the “Command” button and hit “T” to separate the vocal track at this point.
Place your mouse cursor at the edge of this separation and it will automatically change into the trim tool, which looks like a line with an arrow on it. Click your mouse and drag it to the left or right to trim the vocal track. This will allow you to control precisely where the vocal track is chopped.
Repeat this process to chop the vocal track in other places.