We've got a full expansion coming this summer, as well. We'll announce the date for the second bonus pack sometime before then!
One Deck Dungeon has its own full soundtrack, with music for the five dungeons, plus an alternate soft version for each. You can download the full album from Bandcamp, with pay-what-you-want pricing! We just thought it'd be pretty awesome to have a tabletop game with an soundtrack. (It is!)