Flanked by candelabras and clasping a microphone, Scottish Ensemble director Jonathan Morton opened the group's annual Christmas concert with a sing-song. "Let's see what happens when I play this," he prompted, picking out the bass line of Pachelbel's Canon on his violin while the audience murmured along with the counterpoint. He was demonstrating the gist of a "ground" – a pattern that repeats, usually in the bass, while other voices vary around it.

The evening's theme was variations. First came a miniature: the second in a set of four new "musical postcards" by Glaswegian composer Martin Suckling, each specially commissioned to fit the ensemble's concert programmes this season. This latest was called Mr Jonathan Morton, His Ground, a daft name basically indicating that the "ground" doesn't sit in the bass but in Morton's violin part. The piece clocks in at just a couple of minutes, but Suckling's distilled gestures and striking contrasts – bare against sumptuous, busy against still, solo against group, prime harmonies against discord – meant the impact lingered much longer.

Easy, vibrant contrasts marked Britten's Variations on a Theme of Frank Bridge, too. Shifting from chilling quietude to feisty bravura in the flick of a bow change, the watertight ensemble and bright energy made Britten's tribute to his teacher come alive. The concert's second half was devoted to Bach's Goldberg Variations in the arrangement for string orchestra by Russian violinist/conductor Dmitry Sitkovetsky. It's an odd beast. The aria is finely judged, lush and supple with the sustaining power of bowed strings; elsewhere, Bach's counterpoint is brought out in stereo, and there was rustic thrust from the full band and whispered pianissimo from solo lines. The arrangement worked best where Sitkovetsky stuck to one-per-part – not for fault in the ensemble's playing, but because these textures preserve Bach's clarity.

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