There are earplugs on sale at the entrance to tonight's gig and for good reason. Glaswegian noiseniks Mogwai are firm believers in turning it up to 11. But the Spinal Tap comparisons end there.

Will Oldham to Twisted Nerve, the music at this year's Belfast Festival has been selected for its challenging nature. Mogwai are unquestionably not easy listening. Their loud and abrasive post-rock reputation has attracted a crowd of mainly young shaven-headed men - not entirely unlike the band themselves. That's a shame, because in a different setting - and with the volume a shade less offensive - these intelligent and beautiful compositions could appeal widely.

So is Mogwai's music the classical music of its generation? Carefully orchestrated and perfectly executed, the music swings from a battering sonic assault that physically exerts its force to gently picked melodies that you strain to hear.

The bass at times resonates through your bones. Then an unexpected flute melody shies in and all other sound dies away.

Only on very few tracks are vocals used, and even then they're so distorted and frazzled as to act merely as another instrument, not being directly used to convey any message.

However, why do a band that so flagrantly defy expectations of what guitar-based music should be still pander to the tradition of a full-blown workout at the end of their set?

After a superb 50 minutes, Braith Waite heralds "the last song". Thirty-five minutes later - having walked off for the ritual encore applause - the band finally leave the stage. This unnecessary distraction only served to wreak havoc with the momentum and disrupted what was an otherwise well-timed and fluid gig. Where does challenging end and indulgent begin?