"Octahedron" is the upcoming 5th album by prog-rock band The Mars Volta, set for release on June 23. The guitarist Omar Rodriguez-Lopez and singer Cedric Bixler-Zavala have said that it's a more mellow and acoustic album (if you listen to TMV you know that's not their usual MO).
A few songs have been leaked already. Two of them are the singles for the US (SInce We've Been Wrong) and UK (Cotopaxi). Two are acoustic, two are more of the usual TMV rock sound. Most of their singles have been softer songs compared to whats on the actual album (if you're not a fan, mayhaps you've heard their old songs "Televators" and "The Widow").
Since We've Been Wrong (Starts at a certain time because intro is boring quiet wind type noise)
Cotopaxi (probably my favorite of the leaks)
Desperate Graves
With Twilight As My Guide (no it has nothing to do with what you're probably thinking)
As a huge fan, I can't wait for it to come out. Their last album was very fast paced and chaotic, so I suppose a more mellow album is the logical next step, since their sound changes a lot from album to album. The singer is singing more normally, holding back on the falsetto that sometimes turn people off the band. And their new drummer is holding back a lot since the last album, which depending on how much you liked their old drummer, can be a good or bad thing. I'm not that much of a fan of acoustic music, but this is pretty decent.