Great exploration! Also, putting two buckets together and hitting one makes almost a ringing sound. I have the metal handles on our buckets and have my students also play with those to make sounds (hitting, rattling, etc). Hitting the edge of the bucket ----no sticks, just picking up the bucket and hitting it on the ground from different angles also makes great sounds. Stacking buckets and playing the edge like a giant guiro. Sliding the bottom of the bucket against the ground is another one. Playing on the concrete versus playing in the grass. Cracked bucket versus unbroken bucket, hahaha.