The Internet Archive Audio Library has millions of results for free downloads of music, audio, podcasts, radio shows and, most notably, its Live Music Archive.
You can order free music downloads by articles, title, date of publication or more views, as well as filter the results by type of media (concerts, audio, etc.), and themes (for example, rock or funk), language, and more.
You'll find all kinds of artists with free music downloads here, such as Jack Johnson, John Mayer, Grateful Dead, 311 and Smashing Pumpkins.
There are usually several file formats in which you can download the free music, such as MP3 and OGG.
Website: Internet Archive's Audio Library