Britten Sinfonia, Queen Elizabeth Hall, London

So, have performers finally risen up against conductors? Last week, it was the Primavera Chamber Orchestra. On Monday, it was Joanna MacGregor and the Britten Sinfonia, who are similarly interested in seeing how they get on when an instrumentalist provides the direction. After all, that's how it used to be done. There were, however, few other things about this concert that could be described as gimmicky: none of this pianist's special visuals, just some atmospheric lighting.

MacGregor's programme had at its heart two piano concertos composed, as she observed during one of her little audience chats, some four years apart: Alfred Schnittke's Concerto for Piano and Strings of 1979 and Lou Harrison's Piano Concerto with Selected Orchestra of 1983-5. Part of an enterprising 10-date tour, this concert was filled out with Ghanaian and Senegalese music from the percussion quartet Ensemble Bash, plus the inevitable encores, which included some improvisation from both quartet and orchestra.

In the Sinfonia's opening performance of Arvo Pärt's Cantus in Memory of Benjamin Britten, vibrato was gradually applied to moving effect. This was almost the only item that MacGregor couldn't conduct from the piano. With her jerky gestures and gold-patterned jacket, she resembled an exotic bird of prey. She seemed to get the job done, though. MacGregor appears to have no pretensions as a conductor outside such events. But then, a girl can always change her mind.

The mesmerising conclusion of the Pärt was spoilt by the immediate intrusion, initially offstage, of Ensemble Bash's Ghanaian bell piece. OK, so both involve bells, but why ruin one piece to make a point? For all their flair and tomfoolery, Ensemble Bash's performances seemed a bit tired and obvious; it was, after all, their sixth consecutive night on the road.

MacGregor and the Sinfonia, on the other hand, appeared to have energies to spare. The most powerful performance was surely of the most powerful work on the programme, Schnittke's epic concerto. This veers through several changes of mood and speed, with two cadenzas for the piano, but is predominantly dark and introspective. Giving only the most fundamental of conducting gestures, MacGregor demonstrated that a strong interpretative conception can be allied perfectly well to incisive playing without a separate conductor.

Though rivalling Schnittke for idiosyncratic eclecticism, the Harrison, by contrast, makes joyful and uncomplicated use of its specially tuned piano, tone clusters, and rich pickings from world music, adding two harps and three trombones as well as percussion to the strings. It made an excellent main item in the second half, even though it ends somewhat indecisively.

Nitin Sawhney's new Neural Circuits proved to be eight minutes of awkward rhythms that would work better on a synthesiser, plus some banal spoken material on tape relating to 11 September: a first, perhaps, in responding to the present crisis, but scarcely a substantial artistic response.

Friday at St George's, Bristol, the tour ends on Sunday at Brighton Corn Exchange