Here is a looping jam track in the key of A for your soloing pleasure. It’s a nice slow shuffle groove using an A to D chord change that has been at the heart of many great riffs. Here is the audio:[audio:http://guitarteacher.com/media/mp3/jam/a_slowshuffle.mp3|loop=yes]
Some suggested scales for improvising:
And here’s the tablature on how to play it.