Jonny Greenwood's Horror Vacui asked 68 string players to make studio echo by hand.

It closed Prom 70, the first Prom he curated, at the Royal Albert Hall on 10 September 2019. Around the soloist Daniel Pioro, players on raised platforms made reverb and delay with stamping, string slapping and blowing into their f-holes. Greenwood himself played muted bass guitar in Steve Reich's Pulse.