Jonny Greenwood's Horror Vacui asked 68 string players to do by hand what a studio does with reverb.

Horror Vacui, a BBC commission for solo violin and 68 strings, closed Prom 70, the first Prom Greenwood curated, at the Royal Albert Hall on 10 September 2019. The strings do by hand what a studio does with reverb and delay units, echoing Daniel Pioro's line as he plays it.