Smog, Old Vic, London

Smog's Bill Callahan remains an enigma not, it seems, because he won't say anything, but because he can't. His songs of small-town loneliness and romantic trauma share the mordant humour of his fellow American Will Oldham (aka Bonnie "Prince" Billy), with whom he's often compared. But Callahan's painful shyness means that interviews reveal almost nothing, except perhaps that the emotions unsnarled in his songs are unpleasantly real.

He shares Oldham's driven productivity, recently to his detriment: the new album Rain on Lens seems just another bunch of songs, uninvitingly played, his personal reserve making his music forbidding, too. The retreat from Islington's Union Chapel to this smaller (if grander) venue suggests that even loyalists have lost patience with his muted world.

Before he tries to win us back, though, Meanwhile, Back in Communist Russia... provide a taste of their own sordid emotional underworld. This British band's impressive debut album Indian Ink suggests a heavy debt to the seedy sexual monologues of Arab Strap, this time with a girl, Emily Gray, blankly and exhaustively confessing. Her slightly posh voice and cool demeanour recall Black Box Recorder's cut-glass nastiness, too, the voice at its best when it dominates the music's scraped synthetics. When the band's boys self-consciously fall to the floor to smash climactic drill noises, she swings her handbag and leaves. It's too forced, but the talent is clear.

Callahan's self-consciousness is of a more desperate and fascinating order. Backed by an expert, relaxed band, his one stage move is to spread his legs in a guitar-god V, almost constantly. He looks like a posed action doll, with boyish, uncertain features and a strait-laced manner. When audience members attempt conversation, he shields his face with his hand and says nothing. Whatever he feels while playing his songs, he keeps it all in.

The musical reserve of Rain on Lens, though, is swiftly revoked. "Revanchism" is played with a hard-and-fast martial beat, while "Bloodflows", with its dark promise – "Oh, blood will spill, yes it will" – gallops past. The songs are toughened and opened out, swerving from stark country to garage-punk; the lost-love anthem "Cold-Blooded Old Times" crashes into a superfast Jonathan Richman "Roadrunner" riff, and feels healthier for it.

But it's an older song, "All Your Women Things", that reveals Callahan's harsh artistic heart. In it, he lays out the clothes of a lover who's left him with manic care, trying to reassemble what he's lost. "Your right breast," he murmurs. "Your left breast..." And his long pause as Smog play on feels like the next words are genuinely too difficult to speak.

Some banter on his return for the encore shows Callahan does have funny bones in his body. But it's the things he can't say that he says the best.