You might complain that the French artist Yyves Klein's “Monotone-Silence Symphony” is a bit one-note, and you'd be just about right— it's actually just a sustained D-Major chord for 20 minutes, and then silence for 20 minutes. Like Klein's post-war paintings — monochromatic, simple swatches of color — the experimental "symphony" from 1949 is more prolonged tonal exploration or study than arcing narrative. Klein conceived of his "one continuous sound, drawn out and deprived of its beginning and its end, creating a feeling of vertigo and of aspiration outside of time."
The production at Grace Cathedral last month from Dominique Lévy and Brett Gorvy in collaboration with the Yves Klein Archives is the third ever conducted, and was documented by the film production company Slow Clap. Needless to say, the brief clip above is abridged.