Paul Driver finds the combination of the violinist Joshua Bell and the Wigmore Hall's acoustics simply irresistible.

The American violinist Joshua Bell is one of those starry virtuosi - the pianist Martha Argerich is another - who have a weakness for being out of the limelight. Though celebrated soloists, they aspire to the democracy of chamber music. For the past three years at the Wigmore Hall, Bell has been organising brief but vital January festivals of such music with his often equally starry friends, the cellist Steven Isserlis prominent among them. This latest was a Brahms and Mendelssohn celebration, also including a work by Schumann, and, since democracy and even feminism affected the programming, one by his wife, Clara, too, and one by Mendelssohn's sister, Fanny.

The three concerts would be an attractive enough proposition anywhere, but when the illustrious Wigmore acoustics - the one hall in London where a real and genuinely intimate musical experience can be had - are put with the charms of the music and performers, it is not surprising that the series was a sellout, with people standing at the back. There is a truly inspiring quality about Wigmore concerts these days. Here is no attempt to dress up music in media-friendly garments, no projection of players onto screens, no evocative lighting, no ingratiating chats, no dumbing down or talking up, but simply the making of music.

The ritual is timeless. William Lyne, the hall's director since 1966, or a deputy, emerges from behind the stage with a faint flush of excitement. It means the artists are about to enter, but I like to imagine that he has just given them his blessing. A hush settles in. Taking their places beneath the sun rays and blue mosaic sky of the ornate cupola, the players remind us that there are things that can be said by music alone, and this is an audience that wants to hear them.

What this 99-year-old hall, so steeped in a century's musical history and so beautifully refurbished in the early 1990s, offers is so perfect in every way it is amazing that we are not having to fight for its survival. But it seems permanently packed and in rude health. It is heartening, though, that performers of the youthfulness and brilliance of the Bell circle have so conspicuously identified themselves with the place. Isserlis virtually lives here. Others joining Bell this time were the German pianist Alexander Lonquich, the clarinettist Michael Collins, and the Vellinger String Quartet.

It was the last of these that made perhaps the strongest impact. Led by the superb violinist Stephanie Gonley, with a powerful, sonorous cellist in Sally Pendlebury, and Harvey de Souza and Timothy Boulton palpably incisive in the inner parts, this nine-year-old (London-based) quartet has a dynamism, cohesiveness and sheer force of concentration that were manifest in Mendelssohn's ingeniously integrated early E flat Quartet, Op 12, and well nigh overwhelming in his F minor final quartet, Op 80. A stark expression of grief at Fanny's death, the work affords a minor-key experience of the most relentless and tragic sort. The demanding, high-reaching first violin part is more like a yelp of pain. Gonley executed it fastidiously.

That minor keys can be far from tragic is demonstrated by the same composer's D minor Piano Trio, Op 49, a work of amiable poignancy approaching outright jollity, with an A major second subject (in the opening movement) not unlike a music-hall tune. Bell, Isserlis and Lonquich brought the piece off fetchingly and energetically. Lonquich's little solos in the andante were refreshing pools of textural contrast; and with his leggiero touch and vaporising staccati he showed himself an altogether ideal Mendelssohn pianist.

He and Isserlis had prefaced the trio with Fanny Mendelssohn's Fantasia in G minor and Capriccio in A flat (1829), neither of which I had heard before. The latter, written for her cellist brother Paul, was worth discovering: an interestingly shaped movement with an ambiguous tonal shift near the end and a "feminine" close whose gentle uncertainty I took, perhaps fancifully, as a comment on, even an undoing of, the lyrical assertiveness earlier. Clara Schumann's Three Romances, Op 22, with which Bell and Lonquich began the first concert, alas made no impression.

Joined by Isserlis, they ended this programme with Brahms's B major Trio, not the revised text of 1889 but the original 1854 version, in which familiar gambits keep leading into the strangest places; the decisive opening, for instance, into bodyless, almost footling fugal materials. The obsessively self-concealing composer oddly retained the work in his catalogue, and the airing was welcome if unnerving. Unnerving, too, occasionally, was Bell's upper intonation. I put this down to a deliberate effect, but similar moments later in the week had me wondering.

He is a richly expressive player, but his manner implies an E-string sweetness of tone that is not actually there. Still, he led Isserlis and the Vellingers in an account of Brahms's second sextet that was bristling with life; and their reading with Collins of the clarinet quintet made Brahms's minor- key pathos as sublime as ever.