Sleepy Sun performs its namesake track, “Sleepy Son,” at Great American Music Hall in San FranciscoIf there’s one bit of criticism Sleepy Sun might have to answer to, it’s sounding a little too much like their Canadian contemporaries Black Mountain. Not only do Black Mountain’s Amber Webber and Sleepy Sun’s Rachel Fannan howl similarly, but the thundering, pulsing waves of riffage borrow from the same vintage metal and stoner rock bands. It’s sorta like 13th Floor Elevators snuck Iron Maiden some acid and recorded the results. Technically precise guitar work shimmers through the haze of distortion — and even though Black Mountain came first, both bands are equally adept at this — which is why it’s so baffling that Black Mountain can pack out Neumos and Sleepy Sun was merely the second band on a bill with Sleepy Eyes of Death at Chop Suey… on a Tuesday after Fourth of July weekend. I normally find it irritating when two bands with similar names are on the same bill (Sleepy/Sleepy), but in this case, the bands share a similar aesthetic. The difference is that Sleepy Sun relies on technical precision, liberal use of reverb, plaintive harmonica solos and Rachel Fannan’s unearthly wailing, while synthesizers are as indispensable to Sleepy Eyes of Death as butter is to a pastry chef. And yet, the sounds that come out of both bands are definitely related branches on the same Technicolor psych-rock tree. I like Sleepy Sun better, however, because there’s always a sense of movement to the music, even in its sparser moments, whereas Sleepy Eyes of Death tends to meander off on these ambient, downtempo tangents, which makes the music fade into the background so successfully that I stop paying attention. To me, ambient music is like wallpaper: You sort of notice it while you’re looking at it, but you forget it as soon as you leave the room. Sleepy Eyes of Death would transform from a good band into a great one if they would just trim some of those unnecessary chill bits. During Sleepy Sun, however, I was rapt from start to finish, and (assuming I’m not completely projecting my own feelings about the show onto everyone else) so was the rest of the room. Unfortunately, competing with the Chain and the Gang/Golden Triangle show on the day after Fourth of July weekend meant that the Chop was maybe half-full at best, but the folks who were there were intimately familiar with the band’s music. And they proved it when, midway through the set, the entire band paused in one of those fake-out endings that tend to come right before the climax. Usually when bands do this, at least a couple of people who aren’t actually watching what’s happening onstage will prematurely hoot their appreciation before the conclusion of the song. It tends to put a damper on the climax that inevitably follows. But that didn’t happen this time. Everyone was silent. Every single person there knew what was coming (or at least knew enough to keep their mouths shut for a moment). If only there had been more of them.