Proms 25, 26, 20, 21, Royal Albert Hall, London

Last Tuesday, McGegan's San Francisco-based period instruments orchestra, Philharmonia Baroque, made its debut at the Proms with tenor John Mark Ainsley (Prom 25). And if this doesn't change McGegan's profile, I don't know what will. A spirited, stylish, sometimes inspired suite of dances from Les Paladins was followed by a chain of exquisite accompaniments in which the strings bent and curled to Ainsley's authoritative, elegant singing of Handel's "Where'er you walk", "Waft her, angels", and "His mighty arm". In their slightly soggy version of the Water Music, there were times when I wondered how Philharmonia Baroque had landed a prime-time slot when Les Musiciens du Louvre made do with a Late Night Prom. Heard as accompanists - most particularly in the mournful shadows of "Lieux funestes" from Rameau's Dardanus - they more than deserved it.

London Sinfonietta's performance of the same evening (Prom 26) was curiously unatmospheric. Diego Masson's smart, edgy account of Weill's Kleine Dreigroschenmusik fitted the plush velvet dressings of the Albert Hall but would have benefited from more intimacy than this venue could provide. (Ronnie Scott's, perhaps?) Weill's suite made an odd companion to Berio's Coro. This multi-layered, contemplative work is ideal for a building of this size, yet the score floundered under its own solemnity, and the close amplification revealed what might best be termed a mixed-ability group of singers.

No mixed abilities in the Northern Sinfonia, as the first and best of last Saturday's Violins!! Violins!! Violins!! concerts proved (Prom 20). For an event with six exclamation marks to its name, theirs was a remarkably subtle performance; lending pathos to Grieg's faux-baroque Holberg Suite, vitality to Britten's winsome Simple Symphony, and cool glamour to Vivaldi's Concerto in B minor for four violins and cello.

With the cimbalom tones of Bartok's Duos - played by Thomas Zehetmair and Viktoria Mullova - still searing my ears, the second concert of the day (Prom 21) was inevitably disappointing. Martyn Brabbins's natural showmanship encouraged a dynamic performance from the BBC Symphony Orchestra but this supposedly youth-orientated concert was poorly chosen. Invisible Lines - played and created by young musicians from Berkshire, Cheltenham, Gateshead and Southampton - was the strongest work in a patronising programme. If Radio 3 really wants to attract the teens, Andreissen's Snelheid and Adams's Short Ride in a Fast Machine might be better than Respighi's Pines of Rome and Britten's Young Person's Guide to the Orchestra.