Thanks to modern technology, those of us who find that music helps us through the horrible dark hours of insomnia have the record libraries of the world to choose from. Count Keyserlingk, Ambassador to the court of Saxony, didn’t have Spotify to help him through his sleepless nights, but according to legend, he did have the funds to commission a piece from Bach, and his own in-house harpsichord prodigy, Johann Gottlieb Goldberg, to play it for him. Although this charming story is now roundly discredited, the absorbing serenity of the “Aria with Diverse Variations” that now bear Goldberg’s name makes the set perfect late night listening and even the frontispiece of Bach’s published edition states that they were “composed for connoisseurs, for the refreshment of their spirits”. All in all, perfect material for one of Royal Northern Sinfonia’s Late Mix concerts at Sage Gateshead.

Royal Northern Sinfonia sidestepped the eternal question of whether the piano or harpsichord is preferred for the Goldbergs by performing Bernard Labadie’s arrangement for a small string orchestra, plus harpsichord and theorbo. Labadie mixes up the textures very effectively, employing the full ensemble for the more outgoing variations, such as the dances and the glittering French overture that starts the second half of the set, and smaller combinations of soloists or reduced ensemble for the more virtuosic variations – most imaginatively a brittle pizzicato set against the fevered trills of Variation 28 or the plangent theorbo adding a fragile gilding to Variation 13.

I have to confess it took me a little while to settle into the music and I realised, eventually, that it wasn’t the fact that it was the Goldberg Variations being played on strings that was disconcerting me (if I’d had any purist objection to that, I wouldn’t have gone to the concert!), but that I felt as if I was listening to one of the orchestral suites, but with the wrong tunes. To begin with, the players too seemed more at ease in the familiar orchestral world of these dance movements, such as their full-bodied Passepied (Variation 4) and a playful Gigue (Variation 7) but somewhere in the second quarter the music took on a life of its own, flashing by in a whirl of little gems, impossible to pin down.

The solo violin and viola duo of Bradley Creswick and Michael Gerrard made the virtuosic runs of Variations 11 and 18 feel like a bit of relaxed improvisation, whilst another particularly virtuosic variation, number 20 matched the darker singing of second violin Iona Brown against mad chromatic passages on the viola. Some of the livelier movements, particularly in the second half, prompted smiles and laughter from players and audience. Cellist James Craig seemed serenely calm and purposeful even through his fastest passages and Sian Hicks worked her way dextrously round some furious double bass lines, most notably in Variation 12. The penultimate variation, number 29 was an ensemble showcase, the line of music zipping seamlessly between soloists as it worked up and down the stave, interspersed with heavy chords.

The genius of the Goldbergs lies in Bach’s characteristic ability to pull a gorgeous covering over a fiercely strict and rigid framework: there are 32 movements, each variation is made up of 32 bars each derived from the same bass line, and every third movement is a canon. The beautiful human heart of the Goldbergs lies in the slow movements: the aria from which the whole is derived, the gentle loveliness of number 14 or 19 and, above all the dark, haunting despair of Variation 25, famously described by the harpsichordist Wanda Landowska as “the black pearl” of the variations, in which the strangeness of the harmonic writing looks forward to the deep expressivity of later centuries. Bradley Creswick then Michael Gerrard drew out the melody here in long emotional phrases, their muted instruments fraught with the sadness of dark nights.

In its opening appearance, the aria was frail and tender, but it also had a spontaneous, exploratory feel, as if none of us were quite sure where this Goldbergs-on-strings was going to take us. At the end though, after a rousing sing-along of the jolly songs in the Quodlibet Variation 30 that felt like a grand finale, Royal Northern Sinfonia's repeat of this simple aria found it transformed, drenched with a moving sense of homecoming and completion. In the long stillness that followed the last notes, I felt extraordinarily relaxed, as if I was slowly waking up from a deep and refreshing sleep. Perhaps if Royal Northern Sinfonia could just pop round next time I’m awake and buzzing at 3am…