Here’s more evidence to support our view that Twitter in itself isn’t a revolution in music marketing in itself – but just a tool for clever artists and labels to make the most of. Travis Barker and DJ-AM are offering fans a free mixtape download.However, to get it they have to sign in to the dedicated website with their Twitter login, and post a tweet about the mixtape, complete with a #trvsdjam hashtag. They then get to download the mixtape while spreading the word to their friends (well, followers).As you can see by running a Twitter search on the hashtag, the promotion is already spreading like wildfire. But the nice thing about it is that people choose what to say in their tweet – they’re not forced to spam their friends with an automated marketing message. As a commenter pointed out, you’re not able to customise the tweet, but have to go with the pre-decided marketing message.