Create a new music project. When opening GarageBand for the first time, the software prompts you to create a project. Otherwise, you must open the software, click the "File" menu and select "New." Enter a name for your audio project, and choose a key and tempo (speed) below. You can change these preferences later. Click "OK."
Click the "+" button to create an audio track for your vocal recording. Your tracks operate as your recording spaces, and they look like long horizontal bars. The "+" button appears at the very bottom of your GarageBand window, on the left side.
Click the title of your new track to highlight the entire track space. With your track highlighted, click the "Record" button to record your voice. The "Record" button appears near the bottom center of your window and looks like a large red dot. Click the "Space Bar" when you finish recording your voice. You can record using your internal microphone, or with any external microphone connected to your computer.
Click the "i" symbol in the bottom right corner of your project window to open your "Info" pane. At the top of the column is a "Browse" tab and an "Edit" tab. Click the "Edit" tab.
Click the first "Effects" pop-up that you see, just below the "Edit" tab title. A pop-up window appears with a list of the various types of effects available. Click the "Vocal Transformer" effect.
Click the "Vocal Transformer" pop-up, and observe the list of presets -- like "Chipmunk," "Falsetto" and "Droid." Select any preset and click "Play" to hear how the distortion sounds. If you do not feel satisfied with the change, click the pop-up again to select a different preset. Alternately, click the "Manual" option to adjust the individual effect settings and customize your distortion.