I HAVE just one reservation about the performances by the Heath Quartet in the Royal Conservatoire on Friday.

It's just a small concern, though a worrying one, but let's leave it till the end. That apart, the Heath's terrific performance on Friday was enhanced by the group's choice of repertoire, with string quartets by Schubert, Mendelssohn and Beethoven.

Nothing startling there, with mainstream classical masters providing mainstream masterpieces. I feel sure everyone there would have spotted the connection between the three works, but just in case: did you notice all three were in minor key? Schubert's single-movement Quartettsatz was in C minor, Mendelssohn's Capriccio in E minor, as was the most famous work in the concert, Beethoven's opus 59 number 2. Is that important? Did it affect any aspect of the music or the performances?

Yes. I think it provided a broad range of abstract musical characterisations afforded by minor keys that are light years from the old "dark and bright" cliched comparisons of major and minor tonalities. In particular, the Heath Quartet's performances underlined, in both the Schubert and the Beethoven, the interior, discreet qualities the two composers embedded in their pieces: Schubert doesn't always sing, and Beethoven doesn't always shout. Schubert scurried quietly while Beethoven's quartet almost epitomised quiet restlessness, until the catharsis of his energetic finale. And Mendelssohn, that most lyrical of composers, found in the second half of his Capriccio an unflinching fugue of great intellectual rigour.

My one reservation? First violinist Oliver Heath too often puts his intonation under stress with his attack. That's all.