An army of contrabassoons, three tubas, four sets of timpani? Really? Julius Eastman was not prone to understatement, and Proms proved it in last night’s UK premiere of his Symphony No. 2, ‘The Faithful Friend: The Lover Friend’s Love for the Beloved’. The prodigiously gifted and flamboyant Black, gay composer died tragically in 1990 aged 49, afterlife had carried him from the nerve centres of American music – the Curtis Institute and downtown New York with John Cage and co – to alleged addiction and homelessness.

Many of his works vanished. This one-movement, 20-minute symphony only turned up a few years ago in the possession of Eastman’s former lover, the poet R Nemo Hill, to whom it was his farewell. At first it seems closer to Mahler than Cage: a giant lament full of vibrant strings, hefty timpani rolls and deep, dense harmonies.

There’s a strong voice there, from one who well knew the pain of love, and the BBC Symphony Orchestra under Dalia Stasevska’s generous conducting drew out its sorrowful passion before closing in a judder of bassoons. Placing it next to some actual Mahler, however, showed up the plentiful weaknesses in Eastman’s needlessly over-dense and under-contrasted score. In Mahler’s five Rückert-Lieder, less is more, the textures transparent within an orchestra that is large but doesn’t sound it, spotlighting a solitary cor anglais, a spider-web of strings or a glint of piano.

Jamie Barton, the force-of-nature American mezzo-sopran.