An innovative approach to funding new music means that you can literally buy a bar of Charlotte Bray's latest composition. Alfred Hickling investigates, and, yes, stumps up for bar 29.

A sheet of Beethoven's experimental sketches for the Missa Solemnis attracted bids in excess of $400 000 at auction last month. But if 36 bars of Beethovian scribble is beyond reach, you might consider investing in the work of Charlotte Bray, who is selling individual measures of her new work for a tenner.

It makes a peculiar kind of sense - you can buy a bar of soap or a bar of chocolate, so why not a bar of music? The scheme has been conceived by Music-in-the-Round to celebrate the beginning of a residency at CAST, a £22m performing arts centre that opened in Doncaster last year. Usually patrons are invited to sponsor a seat, or have their names engraved on a plaque in the foyer. But Bray's piece enables audiences to purchase their very own moment in time.

The Guardian's bar of Shadow Game, by Charlotte Bray. Photograph: Alfred Hickling

And one of them belongs to the Guardian: bar 29 of the first movement to be precise, which, on despatch of a cheque for £10, arrived as a photocopied sheet of full score by return of post. Viewed on its own, it's a bit enigmatic. The fragment is in C and the main piece of activity in this particular measure is a brisk, doubled line for flute and clarinet. Half the instruments have been allocated a full bar of rest, however, which might seem questionable value for money.

"That's a lovely bar you've got there" Bray says when I call her at her home in Berlin to elucidate. "It's a bit sparse, but it's one of the only times that the instruments play in unison." And what happens next? "It keeps going up" she says. "The flute eventually reaches top E."

That's a challenge for even the most accomplished flautist; but if the supporting parts look a little simpler, it's due to the nature of the commission. The three-movement work, entitled Shadow Game, lasts approximately 15 minutes and has been written for a quartet of professional soloists from Ensemble 360, who will be joined in Doncaster by over 70 musicians from local amateur and youth orchestras.

The solo parts have been written for horn, flute, clarinet and cello in the call-and-response manner of a Sinfonia Concertante: a classical form much loved by Mozart and Haydn, but not often utilised by composers today. "It's very rare to be asked to write for such an unusual combination of instruments," Bray says. "Professional soloists don't always want to share the spotlight, but the great thing about Ensemble 360 is that they're incredibly democratic."

The Guardian's bar of Shadow Game, by Charlotte Bray. Photograph: Alfred Hickling

There are approximately 300 bars in the piece, 43 of which have so far found takers. That still leaves plenty of music to subsidise before the premiere on Saturday night, though the Buy-a-Bar scheme is more of a sponsorship initiative than a fully-fledged crowd-funding exercise. A spokesperson for Music-in-the-Round explains: "The full cost of mounting a new piece of music on this scale is in the region of £11,000, including the composer's commission, musicians' fees and marketing. The majority of that comes from private trusts and public funding, though the bars that have been sold are individual donations that help to offset the overall cost."

That's probably good news for anyone attending the concert without booking a bar in advance. "I'm not actually being paid per measure," Bray says. "So, no, there's no danger that the musicians will go as far as bar 43 and then stop."

• Shadow Game is at CAST, Doncaster, Saturday 8 February. Box office: 01302 303 959.