Linked Horizon (Revo's - the composer's - band; basically, the people responsible for this game's OST) performed a concert of this game's music in Japan. Most of it is on youtube. While most tracks are pretty straightforward live performances of the game's tracks, there's one thing of note. The character themes have been vocalized!

https://www.youtube.com/watch?v=c0v5BY3xmLs
https://www.youtube.com/watch?v=1Rum6BxG1U4
https://www.youtube.com/watch?v=iHdnI1OpsA0
https://www.youtube.com/watch?v=9VJ-cid5t9E