Taking its name from Beethoven's Ukrainian-born patron, Count Razumovsky, it is more than a "flexible" group. Its founder and artistic director, the Ukrainian-born cellist Oleg Kogan, chooses different colleagues for each concert from a pool of freelance soloists and section leaders from world-class orchestras - musicians who share his passion for chamber music but don't always have opportunities to play it. The extraordinary thing is that no matter who is playing, no matter the repertoire - anything from duos to octets - Kogan and his friends earn astonishing reviews and have established a devoted following.
"When I invite new musicians," Kogan explains, "I never demand that they follow my ideas, but try to work according to their strengths. Therefore the chemistry is fresh every time. New communications are always established during the concert, because we aren't stuck with one another! But what we have in common is that everyone has a great deal to give - and we give everything."
It's a heady cocktail of commitment, responsiveness, respect and Kogan's intuitive ability to choose top performers who share a wavelength.
Kogan is joined for this concert by three musicians he describes as "miraculous': the French violinist Philippe Graffin, the Icelandic violist Asdis Valdimarsdottir and the British pianist Ronan O'Hora. The programme includes Beethoven's String Trio Op 9 No 1, Ravel's Sonata for Violin and Cello and Fauré's Piano Quartet No 1.
Kogan is brimming over with plans: founding a Friends organisation; possibilities for innovative recording projects; and an educational programme. This is just the beginning of what seems certain to be an illustrious future.
8 July (020-7935 2141)