In another life Alfred Hitchcock would have been a composer. His use of music in films was revolutionary; his collaborations with Hollywood’s finest musical minds — Miklos Rozsa, Dmitri Tiomkin, Franz Waxman and especially Bernard Herrmann — still stand as the greatest director-composer partnerships in cinema history. But it was more than that. Hitchcock’s understanding of musical form went to the very heart of how he structured his films, like a symphonist whose mastery of emotional suspense was built on acute timings, fastidious cutting and thematic references that could mean everything or nothing.

“Hitchcock changed the way we think about music in film,” declared the American academic Jack Sullivan in his 2006 survey Hitchcock’s Music. “With lesser directors, music is often a form of hyperbole, blasting defensively onto the soundtrack to make up for a lack of pictorial distinction; with Hitchcock, the latter is taken for granted, and music is freed up to create its own realm of meaning, keeping or counterpointing memorable images with sounds that are far more sophisticated than what we hear in standard Hollywood scores.”

Hitchcock wanted the sound of his films to get under our skin. His characters sing eerie ditties, honk noisy car horns and complain that they can’t get certain tunes out of their heads. Hitchcock’s music has its own agency, by turns devious, suggestive and conciliatory. It’s the unseen character manipulating every scene. At pre-release screenings of Psycho shown without Herrmann’s music, viewers hardly reacted to the famous shower scene. It was only once the score had been added — those screeching, stabbing violins, forever shorthand for ‘something nasty is about to happen’— that the scene became unforgettable.

This weekend the BBC Scottish Symphony Orchestra screens the last of Hitchcock’s silent films, 1929’s Blackmail, with live music by composer-pianist Neil Brand. “In my own mind, at least, I have worked with Hitchcock,” Brand writes about the methods he used to compose the score in 2008. He describes a moment halfway through the film when Alice — the heroine who has just killed a would-be rapist — sits on her bed and nervously contemplates her next move. “With the right music we can become Alice, be inside her skin, feel her desperation and share communally the exact moment at which the world changes for her and she glimpses a chink of light down the tunnel. We go from being observers of the action to being willing participants — as is always the intention of Hitchcock’s voyeuristic camera.” Brand reveals that he tried to adhere as closely as possible to classic Hitchcock techniques: in his words, he “consciously emulated what Hitchcock demanded his art should be – pure cinema.”

‘Pure cinema’: for John Butt, Gardiner professor of music at the University of Glasgow and avid Hitchcock fan, that term is intriguingly close to the musicological concept of ‘absolute music’. In a recent essay on Psycho in which he analyses the film according to classical sonata form and early modernist thematic development, Butt suggests that “the film — like so many others from Hitchcock — is suffused with emotional and symbolic hooks that allow the interpreter enormous leeway in finding hidden meanings and implications, exactly the techniques that composers of symphonic and chamber music had been cultivating since the late 18th century.”

It’s a brilliantly unlikely research angle from one of the world’s leading baroque scholars. When he’s not researching Bach performance practice or directing the superlative Dunedin Consort, Butt is planning a book on the relationship between Hitchcock and absolute music. Over a coffee he explains that he started researching the director after realising that what appealed to him about the films was the same thing that appealed to him about certain types of music. “It’s art that has sense and meaningfulness but that doesn’t actually mean anything,” he summarises. “Art that is full of potential meaning, that plays with the human capacity to assimilate meaning, that can work symbolically or onomatopoeically, but that leaves the audience to apply the specific meaning. The composer — or in this case the filmmaker — is betting on our perceptiveness.”

Butt keeps a copy of every Hitchcock film stored on his laptop (“never a dull train journey!” he beams). In the busy cafe he calls up a scene in Psycho in which a car horn repeats the same note that has just been sounded by the strings of Herrmann’s score. “You see?” he says, jabbing at the screen, “Hitch is folding us into the film, creating a universe and finding connections which mean nothing concrete, but which make you think, ‘gosh, I wonder what that means’. It’s exactly what Stravinsky meant when he said that his music meant nothing. I would call it ‘popular modernism’, though I know that seems a contradiction in terms.”

According to Butt, it is “perfectly legitimate” to compose new scores for Hitchcock’s early silent experiments — in fact, for score and film to be “completely independent”. He himself has paired up two of his great passions by watching the Hitchock silents while listening to Bruckner symphonies. “And you wouldn’t believe how often they seem to match!” he exclaims. “That’s because we impart meaning to the film from the music and vice versa.” Which basically allows carte blanche to any film composer wanting to write a new score to a film like Blackmail.

Yet carte blanche is not the approach we’ll be hearing alongside the Blackmail screening on Saturday. The conductor is Timothy Brock, himself a film composer and specialist in live performances of 1920s silent pictures. He studied orchestration with Miklos Rozsa and tells me some of the tricks he gleaned from the Hitchcock veteran: “tricks about doubling, about colour, about what instrument to use to evoke certain feelings. He taught me how to make a small orchestra sound huge (divide up the strings) but above all this: melodically, Hitchcock left everything to his composers, but timing was not up for discussion. Timing was all Hitchcock.”

Isn’t that fearsome rhythmic precision intimidating for any would-be accompanist of his silent films today? “Sure it is!” Brock replies. “We basically have to be just as precise right back. As composer, conductor and orchestrator I have the benefit of knowing the films down to the last millisecond. I don’t use click tracks or time code; with Blackmail I will simply watch the film like anyone else. I have to make it all look spontaneous with the right rubato and such, while in fact it is me going against a machine, cogs driving forward no matter what happens on stage. There’s no room for manoeuvre or error, but it has to feel natural. I guess it’s a bit like hurtling down a ski slalom but making it look graceful.”

Timothy Brock and the BBCSSO perform Hitchcock’s Blackmail with Neil Brand’s score, live at City Halls on Saturday