Alongside composer and musician Jim Fortune and theatre director Matt Lenton, Grierson is creating (for Vanishing Point theatre company and the National Theatre of Scotland) a music theatre piece entitled The Wonderful Cosmos Of Ivor Cutler, which charts the life and work of the mischief-making poet, songwriter, artist and cartoonist, who died in 2006 aged 83.
Cutler was one of the most enigmatic and anachronistic Scottish artists of the 20th century. Asked to describe himself by Irish comedian Dave Allen in 1974, Cutler replied: "I could be described as a humorist, I suppose, but that's more like a job, rather than what I am. I'm a child. Yes, I think that's better."
Grierson says: "The more you listen to Cutler, the more you realise that he loved to take himself apart. He liked to talk about himself in an interested way."
Born to Jewish parents in Ibrox in 1923, Cutler found that his interest in himself was shared by the likes of The Beatles (with whom he collaborated on the Magical Mystery Tour film) and DJ John Peel (who would play Cutler's quirky, comic songs alongside avant-garde bands like The Fall). An anarchistic humanist and a surrealist, Cutler taught primary school children for many years, and lived most of his life in London with his lover and collaborator, Phyllis King.
"He lived politically," says Fortune. "He was genuine, and he was eccentric. He would walk around and pin badges on people. He would throw hundreds-and-thousands around dog poo. He cycled everywhere. He lived according to his own manifesto."
Cutler may have lived that manifesto in London for the most part, but much of his work expresses an affectionate pride in his Scottishness. However, as Grierson points out, he also "liked to take the piss" out of aspects of Scottish culture. This ambivalence most likely came, the actor suggests, from the racism Cutler experienced in Scotland, both during his school years (not least from anti-Semitic teachers) and during early adulthood.
"His biography suggests that he would have been unlikely to have got involved in the Second World War if he hadn't been Jewish," says Grierson. Not only did Cutler feel that he should join the RAF in order to fight against Nazism, but there was particular pressure placed upon Jews to join up - and smear campaigns against Jewish conscientious objectors, due to the dubious notion that Britain was at war "for the Jews".
Although the poet rarely emphasised his Jewishness, on account of his atheism, his cultural heritage does surface in his work. "It's in his music quite a lot," says Fortune. "If you listen to a song like Rubber Toy, it sounds like a klezmer."
All of which makes Cutler both a rich and tricky subject for a theatre work. For a start, there is his wonderfully distinctive voice. It carried a beautifully concocted accent which seemed to owe more to the western isles of Scotland than to Glasgow, where the poet was born and raised. "He described his accent as 'a bastard'," says Grierson. "He said it was made up of Glaswegian, Jordanhill teacher training college and a girlfriend from Islay who taught him 'the hard l'." Trying to perform the poet's voice is "slightly scary", the actor admits, "because everybody's got an Ivor Cutler voice".
If the poet's voice contains numerous influences, his music, which he sometimes described as "primitive", contains a wealth of interests. "It's a funny one with the music," says Fortune of Cutler's songs, which tended to be played, with great simplicity, on a harmonium. "It's simply done, but the more you listen to it, the more you realise it's loaded with influences. There are calypso elements. I can hear Paul Robeson singing sometimes. It's almost gospel sometimes, too. He loved cowboy music, and he loved cowboy films. We're taking a bit of all of that in making the music for the show."
Although they're making an "Ivor Cutler musical", Grierson and Fortune are emphatic that they're not giving the humorist the West End treatment. The show - which will be performed by four musicians, one actor-musician and a further two actors (including Grierson himself) - will attempt to evoke Cutler's "beautiful cosmos" (a reference to the world in which he drank tea with his beloved Phyllis) by staying very close to his own idiosyncratic style.
"We're expanding his songs and taking them as templates," Fortune explains. "We're giving his songs attention, because a lot of them deserve attention; much in the same way that you could make a successful string quartet out of Kraftwerk's music. That said, Cutler's songs always work best when they're played on the harmonium and are stripped down and simple, and there'll be plenty of that as well."
If the show has to flit, magpie-like, between musical styles, it must, says Fortune, be similarly careful not to fall into a single theatrical tone. Cutler was nothing if not diverse in his artistic tastes, and the Vanishing Point/NTS production must be too.
"The guy's a surrealist. So, if you find yourself caught too much in one theatrical structure, you're doing him a disservice. It will have to go somewhere else for it to be truly Ivor Cutler."
The Beautiful Cosmos Of Ivor Cutler tours Scotland from April 4 to May 5. For further details, see www.nationaltheatrescotland.com