As his new work premieres at the First Night of the Proms, Sir James MacMillan talks about the story behind the piece, and his hopes and fears for the future of classical music

Arrive at 11 a.m., Sir James MacMillan instructs: not early, not late. I’ll find out why when I get there.

It’s an idyllic drive across the hills from Glasgow to his home in Ayrshire in the full-throttle heatwave sunshine, past turquoise lochs and fern-green forests. At 11 on the dot I turn into the MacMillans’ driveway, and find myself on a steep road up through the glen with no passing places. James and his wife, Lynne, operate a one-way system in and out, which is why arrival has to be on time.

At the top of the drive sits their whitewashed house, in a glorious spot: MacMillan takes me to have coffee in his upstairs study, with its breathtaking views through a French window over the hills, and across the sea to Arran. He’s spoken many times about how inspiring he finds this setting – he and Lynne moved back to Ayrshire, where he was born, a few years ago after many years in Glasgow – and indeed, here is where he recently finished composing his newest piece, When Soft Voices Die, premiered this weekend at the First Night of the Proms at London’s Royal Albert Hall. The programme is shared with Vaughan Williams’ Serenade to Music, written in ­celebration of Proms founder/conductor Sir Henry Wood, and MacMillan’s new piece is a companion to that; he’s always been a big Vaughan Williams fan, he tells me, even when the music was considered a bit unfashionable.