GarageBand has been the benchmark for beginner-friendly DAWs ever since it was launched in 2004.
A decade on and it's still setting the standard, shipping with a good collection of built-in sounds and loops and sporting an interface that makes it as easy as it could be to use them to create your own songs. There are virtual guitar amps, too, plus support for Audio Units plugins.
Best of all, the latest version of GarageBand is free for everyone who's running OS X Mavericks (itself a free upgrade if you have a compatible Mac), though if you want to add all the content, you'll have to pay £2.99.
This is a ridiculously small amount when you consider that among the goodies that you'll receive for your trifling outlay is the full complement of players from Logic X's Drummer. This is one of several features to have dripped down from Apple's flagship DAW - Smart Controls and compatibility with the Logic Remote iPad controller app are some of the others.
What's more, GarageBand projects can be loaded into Logic Pro X, giving you a ready-made upgrade path should you decide that you need a more powerful DAW. Similarly, projects started on GarageBand for iOS can be loaded into GarageBand for Mac.
In summary, if you own a Mac and want to make music, there's no better place to start.
Download Apple GarageBand for Mac