Sparklite

Beats are these little hidden singing blobs that you can collect throughout the world. Most of the times they hide in holes and you need Wingnuts help to pull them out. Other times they're in bushes or in other breakable foliage.
For me the best way to find them was to turn off the music because even when they're hidden they're singing very quietly. So just enter a stage, kill all mobs and wait a couple of seconds - if you hear a faint singing, they're there somewhere.