Haydn/Holloway/Janacek/Mendelssohn, Endellion String Quartet, Wigmore Hall, London

Like the filled-in gaps in shattered Greek pots, posthumous completions of works by great composers create a queasy effect: the listener looks for the joins, and wonders about the "authenticity" of what has been added. Composer Robin Holloway’s Greek pot consists of the fragmentary remains of the last quartet Haydn embarked upon: two middle movements minus their outer cladding. But Holloway has mercifully abjured the hubristic route of speculative reconstruction: instead he has ‘framed’ the fragment, ingeniously welding in a little clue which Haydn left behind.

As Haydn's superhuman power of invention began to fail, and new commissions became an embarrassment, he devised a curious visiting card to explain his predicament, and he sent this to his publishers along with the half-finished quartet Opus 103. On this card he wrote the first few bars of a part-song he had earlier composed, complete with their text which began: "Gone is all my strength, old and weak am I", and this was subsequently published along with the fragment. Holloway decided to frame the work with a prelude - formed from two phrases in the quartet's minuet - and with a postlude which opened with that song.

Helpfully prefacing their performance with a statement of its theme, the Endellion String Quartet gave this strange hybrid a remarkably convincing premiere. The prelude was an oblique progression of warm dissonances evoking a Bartokian atmosphere, which then segued gracefully into Haydn's typically exploratory Andante. After the Minuet came a brief shift into a subtly alien sound-world - harmonic modulations of a kind not even Haydn could have dreamed of - before resolving into a mode in which Haydn held the floor, with Holloway a spectral presence. The whole thing - including at one point a comical false start by the cellist - felt like a discreetly triumphant experiment.

Continuing their valedictory theme, the Endellions then played Janacek's "Intimate Letters" quartet: written out of white-hot passion for the four-decades-younger woman who had been his muse, this was his final work, and its kaleidoscopic switches in mood and tempo were beautifully captured, if at times too smoothly for the underlying folk inspiration to surface. Then it was the home stretch: Mendelssohn’s String Quartet in A, nobly delivered, followed by a Beethoven encore. Meanwhile the Endellions themselves were celebrating their thirtieth anniversary: many happy returns.