GarageBand, part of Apple's iLife suite, allows you to create and mix your own music tracks not only on your Mac, but on the iPhone and iPad as well. With a full suite of musical instruments at your fingertips, the possibilities of what you can create with GarageBand are endless. The current version of GarageBand for Mac lets you layer and mix up to 255 tracks at once. The Sound Library in GarageBand is also free to use and offers a wide array of tracks, including Apple Loops.
While the Mac version of GarageBand has many more features than the iPhone and iPad version, you can use iCloud to sync your tracks back and forth wirelessly between OS X and iOS. When you're ready to share your tracks, GarageBand supports sharing through email, Facebook, YouTube, SoundCloud, or AirDrop.
GarageBand not only gives you the ability to choose from premixed tracks, but allows you to create your own using on screen controls or by plugging in your own mixing boards, instruments, and mics. Record anything you want from vocals to drum riffs and then use them to create and export your own music tracks right to iTunes.
Aside from creating your own music inside of GarageBand, you can also import existing tracks and create ringtones for your iPhone or iPad. Simply drop the clip in that you'd like to use and cut it down to 30 seconds or less. You can then share it to iTunes just like you would any other GarageBand track. Plug your iPhone or iPad into your Mac, sync your ringtones, and you're good to go.
GarageBand used to come bundled with iLife for $79 but in recent years has become a free offering through both the iOS App Store and Mac App Store. You can grab both versions from the links below. If you want to unlock all the content GarageBand has to offer, you can do so via a one time in-app purchase of $4.99.