BBC Proms Nos 4 and 5, Royal Albert Hall, London <br></br>Errollyn Wallen, Purcell Room, London

If the Proms represent the mainstream, the stream is broad, and doesn't exclude the new. Last Tuesday Leonard Slatkin and the BBC Symphony Orchestra premiered the first of this year's rather sparse BBC commissions, David Sawer's Piano Concerto. Originally announced as lasting 18 minutes, it finally clocked in at 11, and pretty action-packed minutes they proved.

At its opening, soloist Rolf Hind tinkled lightly at the highest keys, while low brass rumbled ominous and distant disapproval. Solo instrument and ensemble had different plans of action, and while the brass led the orchestra into passages of loose-limbed, almost jazzy rhythms, the piano rushed to fill the interstices with its elaborate filigrees.

Momentum increased, generating fractured syncopations that pulsed through the orchestra. The realisation dawned that this was music you might actually want to dance to, yet it wasn't minimalism or crossover, nor an evocation, nostalgic or otherwise, of pre-existing forms. Sawer's title for the movement, "Dancing on the ledge", aptly described the high-velocity vertigo it induced.

Eventually Hind hammered out a sustained low note that ushered in "Scape", the slow movement. Short brass crescendos seemed to grow from the overtones of the piano's well spaced notes as they hovered in the air. While the piano found brief companionship with harp and bells, the strings shuddered hesitantly to life before the opening movement's staccato rhythms erupted once more in a brief but exuberant final flourish.

Sawer said as much as he needed to say, and then shut up. Would that all composers followed suit. Rolf Hind, ever the dapper servant of new music, proved alert to the interplay between sound, rhythm and silence, and Slatkin's unfussy direction got the best from the orchestra that, over the next couple of months, will form the backbone of the Proms.

After the interval, mezzo-soprano Frederica von Stade, one of the vocal superstars of the past 25 years, made her Proms debut in Ravel's gorgeously overwrought Shéhérazade. As she intoned "Asie, Asie, Asie", the opening invocation to oriental excess, a slight tremulousness was already apparent, and throughout von Stade scrambled vowels and blurred consonants, making it difficult to be sure she was singing in French.

Which only goes to show that perfection isn't everything. This was a moving performance, Von Stade sounding enraptured by the music's pungent eroticism, notably during "The enchanted flute", when the instrument's sound appeared to transport her. Then, in the final song, as she considered the eyes, lips and downy features of some sultry youth, her hushed tones seemed to voice an inner, secret arousal. Some of the lustre in von Stade's voice may have faded, but it remains a seductive instrument.

There was more Ravel in the previous evening's Prom, when Myung-Whun Chung and the Orchestra Philharmonique de Radio France stepped out in the composer's volatile La Valse. As the initially sedate rhythm became dangerously distended, a hint of entirely appropriate delirium crept in; we had lurched into some reckless danse macabre that at its climax left orchestra and audience in a state of emotional exhaustion.

The players initially sounded less comfortable with the more celestial timbres of Messiaen's L'ascension. The first movement's organ-like phrases demand secure intonation from the brass choir, but each instrument's entry proved tentative, sloppily co-ordinated.

That the performance eventually found the required intensity was a tribute to Chung's affinity with Messiaen's music.

The highlight of the show, though, was the performance by his sister, Kyung-Wha Chung, of Bruch's First Violin Concerto, which here emerged as bright and exciting as if it were brand-new. Cocking her head to listen to the orchestra, Kyung-Wha Chung gave the impression that she wanted to conduct as well as play, but otherwise sibling accord was complete.

Her luxurious vibrato drew the listener in from the very opening statement, while her graceful phrasing had the improvisatory freedom required to refresh such familiar music. At times her pacing was daringly slow, but there was never any loss of momentum, and if the final movement's big tune was rather sketchily phrased, that only added to the sense of abandon Bruch's wild dance invites.

The will to sample musical life beyond the Proms led me last Wednesday to the Purcell Room, to an evening assembled under the uninviting title "A Dancing Dog's Breakfast". More dance performance than concert, it nevertheless provided a showcase for Errollyn Wallen, an interesting composer whose band, Ensemble X, has a combative motto: "We don't break down boundaries; we don't see boundaries."

To ignore boundaries means running the risk of losing identity, but that is a risk Wallen finds worth taking. The first work on the programme, La Luga, scored for guitar and string quartet, proved the most interesting. At first, the quartet mostly accompanied guitarist Tom McKinney, brief melodic ideas rippling from soloist to ensemble and back again, before an expansive figure for violin was picked up by the cello, and the quartet came briefly to the fore.

Wallen enjoyed the possibilities of contrast between plucked and bowed strings, and her melodic invention proved sturdy enough. During the second movement, Donna Meierdiercks' reptilian writhing added a worthwhile visual counterpoint.

Wallen's tuneful guitar quintet, if not wildly original, answered the challenges which the unusual form sets. I wish I could be more enthusiastic about her songs, written for her own voice and piano, sometimes accompanied by string quartet. Wallen's delivery lacked the grit to make them meaningful. Big vibrato and gospel chord changes do not a soft soul diva make: Nina Simone and Aretha Franklin in her pre-Atlantic days were doing this kind of thing rather better 40 years ago.

Anna Picard returns next week