Youth was everywhere to be seen at the Proms last night. Whether in the massed ranks of Britain’s National Youth Orchestra, soloist Ben Grosvenor (even younger than the precocious Benjamin Britten when he debuted his own Piano Concerto in 1938), Prokofiev’s Romeo and Juliet, or DJ-turned-composer Gabriel Prokofiev, it was an evening celebrating the scope of the teenage experience. Even the Late Night Prom joined in the party, coming courtesy of Nigel Kennedy, still surely the oldest and most defiant teenager in classical music.

Nine out of 10 attempts to feed an audience's visual responses to abstract music are doomed to failure; a great communicator will always conjure stronger pictures in the listener's mind. And there's no doubt that young violinist Alina Ibragimova communicates at the highest level. But here she simply held her own to work in shadowplay with both the mysterious spaces of London's most atmospheric venue and the even more intangible visions of twins Timothy and Stephan Quay. Their film around Bartók's Solo Violin Sonata, though defying intellectual analysis and easy correspondence with the musical ideas, is pure choreographic poetry.

The history of maths and music is the history of early Greek philosophy, medieval astronomy, of the Reformation, the Enlightenment and the two World Wars. While mathematics at its purest may be an abstraction, the quest for its proofs is deeply and definingly human, charged with biological, theological and even political motive. Whether through performance or discussions about music, this year’s Cheltenham Music Festival (which begins this week) explores the mathematical processes that have both shaped and echoed the history of Western Europe and its art, tracing musical development from the polyphonic motets of the 14th and 15th centuries to the Minimalist patternings of Steve Reich.

The two-course evening out is made possible by the Wigmore Hall’s late Friday-night concerts, so if you get out of a central-London show - or dinner - by, say, 9.30, you can add a second layer of entertainment at 10. In my case, a ferociously poor hour spent at contemporary dance in Sadler’s Wells was offset by an hour with Joanna MacGregor in a stimulating splicing of Bach and Shostakovich piano music that at least offered something to think about, if not ultimate satisfaction. Evening not entirely wasted, then.

There must be at least 100 more interesting pianists in the concert world than Lang Lang, but perhaps he is just the best publicist around, because nothing else can explain why such a vacuous display as he gave last night at the Royal Festival Hall could bring a standing ovation. Most of the evening felt like being on a plushly cushioned chintz sofa with Tinkerbell, listening to Bach, Schubert and Chopin being served as a cream tea. Lang Lang Inspires is the slogan at the Southbank Centre all this week, but what is inspiring? His art - or just his vast skills as a public communicator, with 40 million Chinese piano students now credited to the Lang Lang effect?

For the sheer multiplicity of event, the resplendently rich palette of sound and the incendiary aural thrill it detonates, Marius Neset's Golden Xplosion is aptly named. This second solo album from the 25-year-old Norwegian sax player and composer careens between the hyperventilated counterpoint of “City on Fire” and the glacial, slightly ECM-ish soundscape of “Epilogue”.

As Handel’s Messiah is to Christmas so the music of Bach is to Lent. Every Passiontide churches and concert halls are flooded with performances that include everything from dainty consort renderings of the St John Passion to choral societies delivering all but symphonic St Matthew Passions. Mightiest of all, however, is The Bach Choir’s annual concert. Performed on Palm Sunday to a reliably sold-out Royal Festival Hall, it’s a fixture of over 80 years' standing and a rare opportunity to hear the work sung in English. Love or hate the vernacular approach, it’s hard to argue with the sheer force of almost 200 singers accompanied by a gloriously inauthentic, 50-strong incarnation of Florilegium.

Last night Murray Perahia played Bach, Beethoven, Brahms, Schumann and Chopin, and we heard, quite simply, Bach, Beethoven, Brahms, Schumann and Chopin. Nothing more need be said, if one follows the Cordelia principle to love, and be silent.

If you’ve not already read theartsdesk interview with Nick van Bloss, have a look now. Then hopefully you’ll be persuaded to buy his autobiography and this CD. The sleeve notes refer to Van Bloss’s fascination with Glenn Gould’s iconic 1983 second recording of the Goldberg Variations, but in no way is this performance an attempt to imitate Gould.