It’s a golden age for “projects” in pop music. Stars are frequently ciphers for the skills of equally famous producers. Rappers as singular as Jay-Z turn over huge swaths of albums to guests. Mainstream rock acts can be just as singles-devoted as their pop and R&B counterparts.

A pop nation of unattached free agents yields tons of unexpected pleasures. But two young and rising bands in Los Angeles, Health and Entrance Band, are reaffirming the more old-fashioned virtues of being in a band in new ways. “Band”-ness is a different thing from being a guitar-drums-bass rock combo. It’s about being a cohesive unit where each member is distinct and irreplaceable, and where the interplay between them adds up to something singular and new. Entrance uses the pyrotechnic instrumental virtuosity of its three members to aspire to a stoned, Hendrix-sized wallop, while Health explodes practically every trope of punk, noise and electronica and puts the pieces together in almost gallingly ambitious ways. They don’t have much in common, except that each act evokes a bit of that old saying about the Velvet Underground -- that everyone who heard them went and started their own band.