Sifting through the mass of musical material - both finished works and sketches - that was discovered after Charles Ives died in 1954 has kept musicologists occupied ever since. Among the torsos discovered was that of a proposed Universe Symphony, which Ives had conceived as a contemplation, in "tones" rather than music, of "the mysterious creation" of the Earth and Firmament, and of everything within it. He'd begun to put musical flesh on his concept around 1915, and was still insisting that he would complete the project in the 1930s.

Since Ives' death several composers have used the surviving material as the basis for their own completions of the work – a couple have even been recorded. But the concert that ended this year's Aldeburgh festival contained the European premiere of the parts of the Universe Symphony that Ives himself left in a performable state. What Ives scholar James Sinclair conducted, with the Royal Academy of Music Symphony Orchestra supplemented with musicians from the Guildhall School of Music and the Britten-Pears School, was effectively the whole of the first of the three huge sections into which the symphony was going to be divided, together with a short coda intended to end the entire work – about half an hour's music altogether.

The music is utterly unlike anything else in Ives's output. The opening prelude is a huge rhythmic palindrome, involving 20 percussion players, which seems to anticipate a whole range of later 20th-century composers, from Cowell and Varèse to Cage and Birtwistle, while the main part of the movement, depicting the formation of the waters and the mountains, is another vast musical machine of churning string textures, lonely woodwind lines and threatening brass, with groups of instruments (violins in the score, keyboards in this performance) spread around the hall providing an unearthly halo. What the whole work would have been like is hard to imagine, but this is extraordinary enough.