Prom 40, Royal Albert Hall, London / Radio 3

Given the army of scholars enlisted in the classical music industry, you might think there would be no new pieces left to be discovered; yet still they come, unheard messages from the great composers, each a publishing opportunity and a chance to stir up some news.

For Monday's early-evening Prom, given by the BBC National Orchestra of Wales, it was the turn of Schoenberg to receive the revival treatment - on this occasion, the British premiere of a "lost" Notturno for violin and strings, performed in Vienna in 1896 and his earliest surviving orchestral score. And, for once, there might be reason for genuine excitement.

Forestalling alarm in the home counties, let it be said that the piece is wholly tonal, a simple yet soaring salon tune, framed by a prelude that in its turns of texture and harmony already prefigures the richness of Verklärte Nacht. Yet let it also be said (and you read it here first), that Notturno sounds potentially Schoenberg's most popular work, his Salut d'Amour and Valse triste rolled into one. It won't do much for his serious reputation, but it could prove ideal for a five-minute slot of immortality on Classic FM.

Ernst Kovacic gave the premiere, faultlessly, after a heroic account of the Violin Concerto that deserves to be remembered as one of the finest performances of this Proms season so far. Kovacic himself is a remarkable player, able to phrase this music and make its thematic structure crystal clear. In fact, the concerto's severe reputation seems a trifle overdone. Are the "problems" it poses more a case of its concertante structure requiring greater effort from conductor and rank-and-file than is demanded by certain Soviet 20th-century workhorses? In this case, Joseph Swensen's energy, plus intelligent orchestral playing, produced a jewel-like reading.

In the first movement, soloist, woodwind and staccato brass were vital partners in a finely balanced dialogue. Likewise, there was something of the thrill of the circus in the sidedrum preparation for Kovacic's first cadenza in the finale; a foretaste of the second, where simultaneously plucked and bowed notes from the soloist gave some truth to the adage that this was a work for a six-fingered violinist.

Swensen's verve had already worked to advantage in Mahler's Todtenfeier, but his reading of Brahms's Fourth Symphony lacked conviction. Urgent tempi denied the music a chance to breathe, and speak, at its natural pace. Tragedy demands its own speed. In this case, the best advice would have been to make haste slowly.