I recently created these concept illustrations for 'Anthymn', an MMO that weaves the creation and performance of music through the traditional player experience.
Instead of wizards and mages, Anthymn has maestros. Players perform their music in battle, their 'band' of warriors working in harmony to gain combat bonuses. Even the traditional meleee classes sync in as the percussion section, just using the shields and skulls of their enemies as drums. Beyond that maestros can compose warsongs into their songbooks, which work as powerful auras on the battlefield. That age old argument of 'my music tastes are way better than yours can finally be put to the test in battle :)
It's a really interesting concept - and I'm excited to see how the game develops. You can learn more about the project at http://www.theanthymn.com/.