Ever wondered what it is like to be a composer? Sceptical modern audiences are apt to believe that no matter what notes you fling at a page, musicians will play it - an impression reinforced by the apparently arbitrary nature of much modern music.

But the Edinburgh Quartet is in the process of showing music pupils just how much effort it takes to turn an idea into a solid performance. In a series of almost 30 workshops in central belt secondary schools, the quartet is demonstrating that no matter how great the inspiration, nothing can eliminate the labour of creating music suitable for performance.

Earlier this month the quartet returned to Portobello High School, following a visit in November, when it gave a workshop to introduce Higher and Sixth Year Studies pupils to the techniques of writing for a string quartet. With them was Kenneth Dempster, a composer who has written a new piece, “Scattering Tears”, for the quartet and is helping co-ordinate workshops.

In the intervening months a handful of pupils have turned their attention to composing for this unique combination of instruments (two violins, one viola, one cello). Without the glamour of brass or the stamp of percussion, a string quartet must win an audience’s approval with the strength of its musical ideas.

But first it has to be playable. Confronted with a piece by Dave Stewart, who is doing composition as part of his SYS coursework, the quartet had a barrage of questions for the composer. Philip Burrin, second violin, noticed that his part went below bottom G, the lowest note of a violin. Could he transpose it up an octave? Shouldn’t that be a B natural in bar 20? How loud should it be? Where does the repeat go back to?

Dave was overwhelmed. “Do whatever you like, whatever sounds best,” he muttered. He quickly realised that composing is not just an academic exercise in harmony and counterpoint. The sheets of music put in front of musicians are a practical set of instructions in which clarity is all-important.

Eventually the piece was ready for performance. A brittle opening, with fiercely repeated notes on the cello, flowered unexpectedly into a noble tune, propelled from instrument to instrument before subsiding gently to an almost classical conclusion. Dave was thrilled to hear his music so persuasively performed. “I didn’t expect it to sound so good,” he confessed.

Short but effective, the music betrayed the youth of its composer only in the lack of structure. The same criticism could be levelled at pieces by his fellow pupils, Rhona Summers, Nathan Bryceland and Joanna Jeffries, where good ideas suffered from being introduced without any clear point of reference. Like a building, music must have solid foundations.

That afternoon, the quartet moved on to Knox Academy in Haddington. First up was a piece by Paul Kirby, also doing SYS. Following the quartet’s performance came a stunned silence. Not only was this music clearly laid out and immaculately printed (by computer), but it displayed a breadth of emotion and economy of texture that would be the envy of many an established composer. Kenneth Dempster was visibly moved, and had difficulty adjusting to the sophisticated evaluation required for so accomplished a piece of writing.

“Don’t start a piece mezzo-piano,” he advised. “It doesn’t mean anything until we know what piano means.” He turned to the quartet for comments, but all the players really wanted were a few indications of mood and some extra cues to help them come in on time.

Again, structure could have been better, but here it was not so much a case of re-writing as adding more music at the end as a balance. Paul admitted lack of time had forced him to bring the piece to a premature conclusion.

Quartets by Alex Cox and Niall O’Gallagher were potentially as impressive, but were undermined by difficulty of performance. A bewildering number of time signature changes, and unvarying pulse and cyclical melody made it easy to lose track. Computers can write, print, and even play music but the software makes little allowance for clear cues between instruments or easy page turns for players.

At one point the rhythmic complexity of Cox’s quartet seemed gratuitous - although it seemed logical enough in his head, he had found no easy way to notate it. Intrigued, the quartet persevered well beyond the end of the class, but without the satisfaction of a complete performance, something that will have to wait until Knox Academy’s next workshop in March.