Beside me, listening with rapt attention, sat Pat Burke, mother of Richard, the film's writer and executive producer.
A former music teacher, Mrs Burke is also matriarch of a wider musical dynasty that includes her granddaughter, acclaimed Scots composer Helen Grime. "It's almost there," she whispered to me, visibly moved by the experience of hearing the music come to life.
The orchestra, Logan, accordianist Phil Cunningham and two young musicians - singer Hannah Rarity and fiddler Mhairi Mackinnon, from the RCS Scottish Traditional Music Course (of which Cunningham is artistic director) - had just three hours to record the music. The finished product will provide the soundtrack for Whistle My Lad, a short film made by Banchory-based Tripswitch Productions.
Whistle My Lad, which stars Ewan Stewart and newcomer Christy Robinson, tells the story of a doomed love affair between two youngsters whose rival fishermen fathers have been feuding for years. The backdrop is the remote north-east coast fishing village of Crovie in the early days of the 20th century.
Logan's soundtrack emerged from a piece of music he wrote while on an education project with the RSNO on the island of Tiree several years ago.
A former assistant principal French Horn with the orchestra and now head of brass at the RCS, in February this year he found himself at a meeting with Whistle My Lad's producers at the RSNO and the project to write an original film score based on this piece of music was born.
"When we considered the music for Whistle My Lad we thought about a mix of classical - to meet the period drama aspect of the film - and Scottish traditional to give it a sense of place," Richard Burke explains. "The first time the production team heard John's melody Tiree, we knew that having an original score derived from those wonderful, haunting melodies was going to be suit the heady mix of love and tragedy in our story."
"I spent time at the Whistle My Lad shoot at the beginning of this year on the Banffshire Coast," Logan adds. "I could hear the melodies I had written and the waves coming crashing in. It felt like it was meant to be. So I then went off and married it all together."
Recording film soundtracks is nothing new for the RSNO. It was one of the first orchestras to record movie soundtracks for commercial purposes, mainly through the Varese Sarabande label. These included works by Elmer Bernstein, Bernard Herrmann (it won a Grammy for its Vertigo soundtrack recording), Jerry Goldsmith, Franz Waxman, John Williams and John Barry, several of which were conducted by the original composer.
Despite this track record, the only original movie soundtrack the RSNO has recorded was Craig Armstrong's composition for Peter Mullan's 2002 film, The Magdalene Sisters.
When the orchestra moves out of its current base in the west end of Glasgow to its new home next to the Glasgow Royal Concert Hall next year, the hope is that its ability to record original movie soundtracks will be greatly improved.
Having Phil Cunningham on board for Whistle My Lad encouraged the orchestra to be more sympathetic to the folk music element in Logan's composition, something a London-based orchestra might not have grasped. The accordionist is also convinced there is scope for Scotland to have a home-grown speciality in providing original film scores for cinema.
"It is not often you get the opportunity to record with a full orchestra," he says. "Soon we could be supplying Hollywood with all its requirements..."