ReverbNation is more than a website builder, it started off as a MySpace alternative and now offers everything you'll need to promote and sell your music through email, Facebook and other channels.
The website builder is secondary to their main goal of becoming the hub for all your promotion and marketing needs. You only get the website builder with their Premium Plan (19.95/month), which is a bit pricey if that's all you're going to use. But that would be a shame, since the Premium Plan also includes features like distribution on iTunes, Amazon, Spotify and dozens more, plus a free domain name.
The free option is just a ReverbNation profile page to keep in contact with your fans and also sell your music, but it's ad supported.
In conclusion, if you're only looking for a site builder, keep looking, but if you want the whole package, try it free for 30 days (credit cart required)
