In the last decade of his brief life Felix Mendelssohn juggled artistic exploits and obligations in London, Berlin, and Leipzig. He founded (what was then called) the Leipzig Conservatory in 1843, where he taught composition alongside faculty that included Ignaz Moscheles and Robert Schumann. In the fall of 1844 he decided to take an extended holiday from this juggling act, and the Mendelssohns temporarily moved to an apartment in Frankfurt – where the composer allowed himself to relax and focus on writing. “These are happy days,” he wrote to his brother Paul.

It was there, in the summer of 1845, that Mendelssohn wrote his Second String Quintet. One of eight chamber works he composed in the 1840s, and one of his last, the Quintet holds several distinctions – not least that Mendelssohn chose not to publish it. The reason, it seems, was because he simply didn’t like it enough. Mendelssohn told Moscheles that he considered the finale, in particular, “not good.” It was published posthumously in 1851.

The autograph score appears almost as a final draft, with very few markings, which deepens the mystery: why did Mendelssohn leave it on the shelf? In answer, perhaps, are the composer’s own words to J.C. Lobe – a contemporary who interviewed Mendelssohn – to whom he acknowledged he would sometimes make himself finish a piece despite his disappointment with it. “Though not an art work in the highest sense,” Mendelssohn said, “it is still an exercise in forms and the representation of ideas. Here you have the reason why I have written so many compositions which have not and never should be printed.”

Sometimes, though, the art is more important than the artist’s humility about it, and this Quintet is appreciated today as a strong chamber work from the latter end of the composer’s life. It is also the signpost of an evolving style, the growing pains of a composer freeing himself from contrapuntal writing and classical embellishments and pursuing more overt and dramatic expression.

The prominent attribute of the Quintet is energy. Immediately, fierce tremolo gales blow through the Allegro vivace, ushering in a sprightly rising theme. Eddies of triplets swirl and froth around the idea and, though the proceedings intermittently relax into a gentle, descending motif, the leaping theme rushes back in for a lively coda. The Andante scherzando changes the pace – mixing a light, courtly waltz theme with moments of devilish pizzicato.

Some of Mendelssohn’s most sober, tragic writing is contained in the Adagio e lento – weighty chords swelling over a trudging cello line. And although this movement slows the work to poignant reflection, the energy remains in an intense, insistent rhythm that pervades, and it all climaxes with wild tremolos quaking beneath a high violin line. The Allegro molto vivace is what, apparently, gave Mendelssohn enough trouble to abandon the work – many have pointed to the absence of contrast in what starts out as a sonata-rondo form, rendering it the only monothematic finale in the composer’s canon. Ignoring its author’s disappointment, though, the finale hurls the Quintet back into action, serving up the most blazing rhythms yet for a rapid dash towards the finish line.