Cellist Steven Isserlis gave a deeply-emotional performance of Schumann’s Cello Concerto with the Scottish Chamber Orchestra to a mesmerised capacity audience in the City Hall a week ago last Friday. During the interval, I overheard a younger member of that audience describe Isserlis as The King of Soul, which was rather nice.

Such was the reception, an encore was clearly in demand. Isserlis made a short announcement which I didn’t fully hear, except that it was something by Sally Beamish that had a Catalan connection. It was so incredibly beautiful and soulful that my heart ached. I was just going to let it go: back to base and get thinking and writing is always my imperative after a gig. But I was held up as numerous people asked me what the encore was and what I’d thought of it.

Then, in Edinburgh last week, at another event altogether, somebody buttonholed me and asked what I knew of Isserlis’ encore. I thought I’d better find out, and so emailed Sally Beamish. It was called El Cant dels Ocells, The Song of the Birds, a traditional Catalan lullaby and Christmas song which tells of Nature’s joy at the birth of Jesus in a stable at Bethlehem.

It was brought to fame outside Catalonia by the great cellist Pablo Casals, whose instrumental version for cello, with piano or orchestral accompaniment, was made after his exile from his homeland in 1939. He would begin each of his concerts by playing this song. It’s often considered a symbol of Catalonia.

Steven Isserlis had his eye on it as an appropriate piece for an encore, but it was unsuitable as it needed either piano or orchestral accompaniment, and couldn’t therefore be used as a spontaneous solo encore after a concerto. So around 1998, Isserlis asked Sally Beamish to write a solo version of the piece, and that’s what we heard as his encore in Glasgow. Isserlis has also recorded it on his Bach Cello Suites CDs.

Beamish herself, celebrating 25 years in Scotland as a full-time composer, is on a bit of a roll. A new CD devoted to her music on the Swedish BIS label, with performances by the RSNO, National Youth Orchestra of Scotland and conductor Martyn Brabbins, marks her astounding productivity with recorded performances (dazzling ones, too) of three of her multi-faceted concertos, each with a glittering soloist: James Crabb plays The Singing, an accordion Concerto, jazz saxophonist Branford Marsalis plays Under the Wing of the Rock, adapted specially for him by Beamish from her piece originally written for violist Lawrence Power, while superstar trumpeter Hakan Hardenberger plays Beamish’s stellar Trumpet Concerto.

Topping out this lot are two orchestral pieces, the evocative Cage of Doves and Beamish’s off-the-leash case study for young virtuoso musicians, the rumbustious and appropriately-entitled Reckless. And there will be more in the immediate future, as her 60th birthday looms next year. But for now, Beamish can scarcely contain her excitement at one development, and a surprise one, too. “I’ve taken up playing the viola again.”

For those who don’t know, Sally Beamish, before her permanent move to Scotland in 1990, was a well-established, London-based viola player who had played in the Academy of St Martin in the Fields, among other groups, and indeed, in 1987, was principal viola in the Scottish Chamber Orchestra. From 1990, when she moved to Scotland as a full-time composer, playing took a back seat and faded. Her children grew up and one of them, Sally’s daughter Stephanie Irvine, is studying violin-making at Newark College. During her gap year, and on an apprenticeship, Stephanie made a viola. The deal with her mum was that the viola would need to be sold to pay for her tuition. After some thought, Sally decided to buy Stephanie’s viola herself, thinking she might hand it over to a young player who needed a good instrument. “So I now own a viola again, after all these years.

“But by an extraordinary coincidence I was invited to play at a festival in the Swiss Alps this August by cellist Xenia Jancovic, who didn’t know I no longer played. So I decided to go for it!” Apart from anything else, it was classic brass neck. One assumes that Beamish more than got away with it, as she’s been asked back next year to play in, among other things, Schoenberg’s Verklarte Nacht. “So now my day starts with practising scales, exercises and Bach!”

Not that her composing has taken a back seat, with a ballet, The Tempest, coming up at Birmingham, a 40-minute work for Ex Cathedra to be premiered in Stratford on the eve of Shakespeare’s birthday, and her first Piano Concerto, for Ronald Brautigam and the Amsterdam Sinfonietta. Multi-tasking, or what?