Every time we hear about Adventuredrum, it’s like the group is that legendary fish that got away — it’s a consortium of 15 drummers! No, 20 drummers! No, 25 drummers! The musicians, a wide range of veterans from a bunch of quality bands (Ted Leo and the Pharmacists, Dirty Projectors, Pattern is Movement, Bardo Pond, Many Arms) loosely organized by Man Man percussionist Chris Powell, seem to use the term “Adventuredrum” both as a formal band name and an occasion — as in “the next Adventuredrum.” They’ve had only one show so far, back in March at the PMA; there was a whole lot of dancing involved, especially given that (we’d guess) most people there were stone sober. Powell says that this second show will involve “probably 25 people” and a bunch more drumsets than the measly three at the first show. They’ll also be extra celebratory, as Ricardo Lagomasino (Many Arms, The Sea Around Us, Joe Lally) is getting married earlier in the day. (“Weddingdrum!”) It’s likely to be at least another six months before the schedules of two dozen busy working musicians align for a third show (much less one that’s free and outdoors), so catch this one while you have the chance.

Sat., Aug. 25, 6 p.m., free, with Ollin Yoliztli Calmecac, 40th and Walnut streets, universitycity.org.