The décor was already in place: Persian onyx bar top, gold Greek-key furniture detailing, lots of velvet and fringe. A “heavy, older kind of setting,” is how the composer, who is 34, described it.

A resident of L.A. who was born in Tel Aviv and educated at Berklee College of Music in Boston, Mr. Blumenthal researched the Plaza project by prowling New York’s hotel bars with a colleague. He was not impressed. “You hear a very narrow sound image so everybody can speak and make noise,” he said. “That’s it. The whole night. On the other hand, when you go to a club, then you hear all the low end—the beats and all that. What we’ve created here is something much more dramatic.”

The four tracks Mr. Blumenthal has composed for the Rose Club include a “Plaza theme”—embedded, he said, because “they didn’t want it to feel too commercial.” By the bar, the beat is louder and more insistent; next to the staircase on the lower level, the sound is muted enough to permit conversation. And off in an enclave he has dubbed “the stoner corner,” one hears lots of bass and guitars and not much else. “You won’t be able to play this mix in any other room,” he said, “because it’s mixed into this specific setup of these specific speakers here. The music is kind of embedded in the wall.”