As a successful progressive rock musician in the 1970s, David Jackson knows a thing or two about the importance of the visual spectacle in musical performance. So for his newest work to be based around “invisible instruments” might not be what you’d immediately expect.

But these instruments, developed especially for severely physically disabled youngsters unable to play normal instruments, are being used by the stars of Twinkle, a musical about how the constellations of stars came about.

The show premiered at The Anvil Theatre in Basingstoke, Hampshire, this week when about 100 children from four Basingstoke primary schools took to the stage. But it was the 12 nine to 15-year-old pupils from Treloar, a special school in nearby Alton, who commanded most attention with their invisible instruments soundbeams.

These resemble the theremin, a musical instrument played without physical contact, with electronic signals rather than keys or strings. The child waves an arm through the various beams, which trigger sounds, notes or chords stored by David.

The performers then improvise as soloists in the midst of the rest of the composition, which is sung and played on regular instruments by the mainstream pupils.

It is the culmination of a long musical journey for David, now 60, who played the saxophone in progressive rock band Van Der Graaf Generator from 1969 to 1977, rejoining them occasionally since. From the 1980s onwards he was a maths teacher and then a freelance music specialist working with disabled children and adults.

“I used to write a lot of pieces for performance in class, as well as make instruments for children, things such as pan pipes,” he says. “This was before the national curriculum, when one was largely left to one’s own devices.”

This spirit of making the most out of whatever is available went a long way. When he arrived at Treloar in 1999, somebody had left behind bells that were due to be thrown out. David salvaged them and composed a piece that they premiered at The Anvil before taking the show to London.

The new show is based on Greek mythology, though with a modern slant. “In the story, the constellations are created by the gods of Olympus to please Zeus, the supreme god, who was bored with the night sky being so black,” says David. “Zeus is very much a Sir Alan Sugar type, firing the other gods if he’s not satisfied with their efforts.”

David had to make a selection from the Treloar pupils he has been working with since last September, whittling potential candidates down to 12 performers, plus three understudies. His criteria were not as brutal as The Apprentice. “I selected the children who needed it the most, in terms of emotional state and self-esteem,” he says.

Sally Mack, a part-time teacher in the music department at Treloar, has been closely involved with the pupils using the soundbeams. “It gives those who have limited ability the chance to play music independently,” she says