Any show at Bottom Bracket Social Club is worth checking out. There’s a mystique to the little DIY space that makes it truly feel like you are a part of some underground movement. And then, of course, when the place serves up hefty helpings of live music by talented locals, there’s basically no excuse not to roll through. Case in point: this weekend’s show featuring Roshii and Collective Dreams, two bands that deserve a bit of your attention even though they don’t often get much of the local music spotlight. With both acts, it’s all about the music. Roshii, for its part, makes an unlikely (but potent) cross between funk, punk, math rock, and alternative rock (dig roshii.bandcamp.com to hear how that works). Collective Dreams, which you can hear at soundcloud.com/collectivedreams, make dreamy, experimental rock music that’s jangly and sometimes even danceable.