Proms 39 &amp; 40, Royal Albert Hall, London <!-- none onestar twostar threestar fourstar fivestar -->

Mozart, Mozart everywhere but not a Mozartkugeln - those delicious chocolate balls - to eat. As the master continues to be played remorselessly down Kensington Gore, someone's missing a commercial trick.

And there was little remorse about the packed weekend performances given by two multinational youth orchestras. Mozart, the writer of violin concertos, was the link - we heard three of the five all written in the same year, 1775 - as well as the utterly remarkable Sinfonia Concertante for violin and viola.

Janine Jansen (Prom 39) kicked off with the last of the concertos, in A major, with a reduced European Union Youth Orchestra conducted by Vladimir Ashkenazy. There was a delightful spirit of comradeship between soloist and orchestra, she swaying round to catch the oboes - although at times losing her sound as she did so. Jansen's a neat, spirited player with a nice sense of the unexpected, colouring Mozart to suggest that things are not always as jovial as they seem. The slow movement, which should bring tears to the eyes, lacked intensity, but in the "Turkish" episode of the last movement, she and the cellos had a great time.

Maxim Vengerov was both violin soloist and conductor with the UBS Verbier Festival Chamber Orchestra (Prom 40). In the Proms premiere (!) of Mozart's first D major Concerto, his super-refined sound and sweetness at the top of the instrument were, as ever, awe-inspiring. But it was with Lawrence Power in the Sinfonia Concertante that real magic was made.

Power, who seemed to have the greater sound, gorgeously coppery in colour, was the perfect partner - a Papageno to Vengerov's Tamino. During the achingly sad slow movement, goose bumps abounded.

I suspect that the orchestra could have released Vengerov from conducting duties in the concertos, and might have played more gleefully in Mozart's 29th Symphony if Vengerov had let them off the leash.

The huge EUYO, however, needed a ringleader in Shostakovich's massive 4th Symphony, even if Ashkenazy failed to raise the last bite. This is a crushing work, deathwatch-beetle clicks leading to a death march. Heart-wrenching to witness such profound performance from such young musicians.

BBC Proms to 9 September (020-7589 8212; www.bbc.co.uk/proms)