Noting Is Real (Strawberry Fields Forever) (1990) by Alvin Lucier:
A documentation on Eliane Radigue. She mentions how she places loudspeakers in the concert hall at 9’55”:
Hildegard Kleeb performs Music for Piano with Amplified Sonorous Vessels (1990) by Alvin Lucier, also available on the CD Panorama, with other beautiful works by Alvin Lucier:
A Letter from Schoenberg (1996) by Peter Ablinger.
Listen first to the version without text:
And listen now to the version with text added: