Open GarageBand. If you have not created a new project previously, GarageBand will automatically prompt you to create a project. Enter a title, such as "My Hip Hop Beat," in the "Name" line and choose a tempo using the "Tempo" indicator below. For a slow beat, try for about 90 to 100 beats per minute. For a mid tempo beat, try the default tempo of 120 bpm, and for a fast beat, try a tempo between 140 and 160.
Click the "+" button in the bottom left corner of the project window to create a new track. GarageBand, like most professional studio environments, arranges recordings according to "tracks," each of which represents a single layer of the overall recording, such as melody, percussion or bass.
Click the "Loop Library" icon in the bottom right corner of your screen to open your loop library, which contains your audio samples. You will then see two lists of loop categories. The first category contains instrumentation types, like "Drums" and "Synths," while the second list contains moods, like "Cheerful" and "Relaxed."
Click the "Drums" option to begin with your percussion, and choose a mood from the second list in the Loop Library, based on the type of beat you want to create. Alternately, use the white "Search" box at the very bottom to enter your own specific classification, like "Hip Hop" or "Rap," to see a list of relevant loops.
Sample the drum loops that appear on the list. Click the title of any loop to hear how it sounds, and click it again to stop. A strong percussion is the foundation of a good hip hop beat, so when you find the perfect loop, click the title and drag it onto your blank audio track, which appears near the top of your GarageBand window, resembling a horizontal bar.
Create a second track and choose a bass loop from your loop browser. Like strong percussion, a solid bass line is essential to a good hip hop beat. When you find the right beat, drag it onto your second track. The bass loop region (the shaded part of the horizontal bar) should appear aligned just below the drum track, so that they play in unison. Add additional tracks with more layers based on your own needs. For instance, add a keyboard loop for melody, or add sound effects for added dimension. GarageBand allows you to add as many loops as you need.
Repeat your loops. A typical loop spans a length between four and 16 bars, but you can cause them to repeat as many times as you want. Just click the lower right corner of the loop region and drag it to the right. It will continue to stretch along the time line. Stop dragging after the loop repeats as many times as you need. Stretch multiple loops simultaneously by highlighting all of them with your mouse and then dragging any one of them.