A co-production between the T'ang Quartet and Glasgow-based Theatre Cryptic, Optical Identity was commissioned by the 2007 Singapore arts festival and subsequently performed at this year's Edinburgh festival. In recent weeks, the Singapore-based T'ang Quartet has returned to Scotland to tour the production, taking in some unlikely venues in isolated communities.

Theatre Cryptic artistic director Cathie Boyd's experiments with the visual presentation of music mean that this production is as far from a conventional string quartet concert as you can probably get. A common flaw of many of Boyd's Cryptic projects has been that the music hasn't been good enough to merit having such extraordinary attention lavished on it or to make the video projections, sophisticated lighting and theatrical elements of the production cohere into something meaningful.

Optical Identity's repertoire is stronger than most: it opens with a fairly classic contemporary quartet work, Kevin Volans's minimalist White Man Sleeps, and proceeds via contrasts: Rolf Wallin's punchy Phonotope I for quartet and electronics; the mesmerising eastern exoticism of Franghiz Ali-Zadeh's Mugam Sayagi and Joby Talbot's playful Manual Override.

Boyd brings to this her customary treatment of dramatic lighting effects and screen projections, with the T'ang Quartet's members - who have committed most of the programme to memory - moving around the stage space as they perform. The effect is somewhat akin to a high-budget rock concert. It's not an approach that would work with anything but the most contemporary end of the quartet repertoire, just as it isn't every string quartet you would want to see in the T'ang Quartet's midriff-baring structural white outfits. But it is particularly effective in the electronic works, the visual elements bringing out the dramatic, spatial effects of Phonotope I in the way that a conventional performance would not.