The sun is out and the musical migration has begun. Many metropolis music venues decide practically to shut up shop for the summer, and the concert junkie needs to uproot and search out top classical music at one of the summer festivals that spring up seasonally. So I left Bristol bright and early for a mid-morning concert at the Pittville Pump Room, Cheltenham Music Festival’s elegant neo-classical venue that immediately conjures up images of ballgowns and Jane Austen characters, perched as it is at the top of a prettily groomed park.

Whilst those early 19th-century audiences might just about have managed the second work on BBC Radio 3 New Generation Artists the Signum Quartet’s programme – Schubert’s String Quintet in C – I’m sure Britten’s String Quartet no. 2 in C would have left them bemused, if not totally bamboozled. As festival director Meurig Bowen announced before the concert, the Signums learned this piece at his request in honour of the festival’s celebration of birth-year boy Benjamin, and they brought a certain freshness to this ephemeral chamber work of 1945.

A feature of the Signums’ performance throughout the concert was their perfect evenness of tone, which was striking from the off, Britten’s unison introduction being played in a beautifully measured fashion, filling the tall domed room with a mysteriously distant sound. The individual lines separated, grew and disintegrated, floating into the ether, the music just being pinned together by growingly persistent inverted pedal notes. Kerstin Dill’s first violin eventually broke free from this sparse but insistent texture with a soaring melody, but a musical idea was never allowed to settle for long. Britten’s music is not bound by the rules of gravity, and the intense quality of stasis the Signums infused into the final chords of the movement had a similar effect on me; an incredible feeling of weightlessness and serenity seemed to take over my whole being. It was extraordinary.

The second movement is a far feistier affair, with busy lines sounding over fiercely accented rhythmic accompaniment. The Signums’ amazing homogeneity of sound returned at the beginning of the third and final movement, a “Chacony” in which each instrument (with the exception of Annette Walther’s second violin) takes up an increasingly prominent role before diminishing after an individual cadenza. If this sounds formulaic, it most certainly was not: the Signums’ freshness combined with the volatile musical texture to lend this performance an air of impassioned spontaneity. After an impressively dexterous final cadenza from Dill, the opening unison melody returned, shot through this time with radiant doubled-stopped major chords. These bursts of sunlighted interrupt the musical flow repeatedly, eventually engulfing everything, as the piece concluded with repeated bow-wielding flourishes from the players.

After an exceptionally agreeable interval stroll around Pittville Park, I returned to see Leonard Elschenbroich join the Signum Quartet for Schubert’s String Quintet. Schubert’s additional cello is vital both texturally and melodically, and enjoys frequent antiphonal exchanges with the first violin throughout the piece. This lent a lovely visual symmetry to the performance, with a particularly joyous-looking Xandi van Dijk providing the bridge between the cellos on his left and the fiddles on his right. This visual balance was matched by an aural one: Elschenbroich’s arrival if anything enhanced the quartet’s signature equality of sound, which was again wonderfully evident in the first movement’s light opening passage. The tranquillity with which this first movement ended spilled over into the second, in which the three internal players provided a stable framework on which Dill and Elschenbroich could play. Whether simply holding static chords, or providing rhythmic impetus by dramatic hemiolas, the three inner players were the beautiful beating heart of this slow movement. The Scherzo is far less refined, with the open strings of both cellos thrumming away rustically. The texture thins in the trio, viola and cello playing a melody in octaves before the music drops into an expansive major sonority. An impish rhythm creeps out of some dark-hued chords and leads the music back into the rustic romp, ending on an almost applause-inducing flourish.

In the Finale, the players really began to show their enjoyment, relishing the rhythmic drive provided by a syncopated accompaniment. Schubert plays around with the rhythms in this movement, keeping the audience on its toes by switching between straight and dotted recitation of the returning rondo melody. A return to the sumptuous high cello duet from the first movement appeared to draw the music back in time, before the ensemble took off again, feeding off the movement’s energetic opening material to propel the music to a magnificent conclusion.

This was a concert experience to prove many things: the genius of Britten and Schubert; the brilliant talent of the Signum Quartet; the excellent programming, scheduling and general quality of the Cheltenham Music Festival; and the mantra that everything’s always better when the sun is shining.