I'm trying to find the title for music containing all percussion instruments (pianos/xylophones not included) such as drum corps and marching band drum breakdowns. I'd basically like to listen to music completely consisting of drum beats. What would one call this genre? If I wanted to listen to this on Pandora, for instance, what would I put in the search field?
Percussion, by definition, includes pitched percussion. So it sounds like you're looking specifically for "non pitched percussion music".
Some descripting terms that come to mind might be drum circle, drum line, rhythm music, street beats, african drumming.
I would just call it "Percussion music". Google does seem to return results for that.
See also percussion ensemble and drum troupe.
I would start on Pandora searching for an actual percussion ensemble. A good start would be So Percussion. Then continue to like their music.