It was done the next night.
Here it is knit up:
I used two balls of Zitron Nimbus and US 10 needles. I cast on 6 stitches, joined in the round, increased 6 stitches every round until I reached 48 stitches, purl a couple rounds, then knit a long tube. Cast-off most of the stitches, then made a long strap on 16 or so stitches to use up the rest of the yarn.
I ran it though a couple hot, soapy cycles in the washer. Pressed the water out and dropped a couple straight drinking glasses into the tube to shape it while it dried. It ended up being about the size of a Pringles can.
We figured out where/how it would hang from his drum kit before I sewed on a big button and cut a slit into the strap for the button.
So the idea is: as he's drumming, if a stick flies out of his hand, he'll have another within easy reach to pull and continue playing on.
Now... back to the mittens :(