Annea Lockwood’s eerie, droning soundtrack is a highlight of the opera-film History Of The Present. Now in her ninth decade, this legend of improvised music and sound-art created the work by ‘playing the Peace Lines’, as she described it prior to an earlier screening of the film in Belfast. By attaching geophones to the huge, corrugated metal barriers that divide up communities across writer Maria Fusco’s home city of Belfast, the composer and field recordist was able to eke strange, unearthly swellings of vibrations from the walls, which remain potent symbols of division and trauma for many Belfast residents.

Born in New Zealand in 1939, Lockwood moved to England in 1961 to study at the Royal College Of Music, with summers spent in Darmstadt, Germany, then a hub of experimental classical composition. Inspired by figures such as Pauline Oliveros and John Cage, her early work extended ideas around experimental performance. For her iconic Glass Concert of 1968, Lockwood and her partner struck and smashed a range of glass objects and hangings in front of a live audience, periodically performing in total darkness.

She has also long been drawn to environmental recording, tapping into the hidden sound-worlds of natural objects and environments. Working on a film tracing the emotional impacts of the Northern Irish troubles presented a very different set of possibilities, obliging Lockwood to think about the sound-worlds of objects and environments much more impacted by (and symbolically connected to) human activity.

‘One of my first questions to Maria when I came on board was, “when the wind blows, do the Peace Lines make sounds?”’ says Lockwood. Fusco replied that they were ‘too massive’ to move in this way. However, working with experts from Belfast’s Sonic Arts Research Centre, Lockwood was able to use geophones (devices that convert ground movement into voltage) to create collages of yawning, heavy, low-frequency noise. ‘We were actually able to learn how to play the walls,’ she recalls. ‘It felt like learning how to play an instrument. And they made extraordinary sounds, just from the slightest movement on the surface.’

History Of The Present is centrally concerned with ideas of repressed or deferred speech. Suitably enough, much of Lockwood’s composition has the quality of thwarted or stilted vocal communication, as if a human voice had been trapped within the Peace Lines. For visitors to the Edinburgh Art Festival performance screening of this film, the prospect of live improvisation from percussionist Angela Wai Nok Hui promises a still more intriguing and immersive experience.

History Of The Present, Queen’s Hall, 11 August, 8pm.