The recordings of Prokofiev's Sonatas No. 9, 8 and 4 are derived from radio broadcasts in Germany (1964), Switzerland (1971) and Turkey (1973) and that of the Toccata from a Soviet Union radio broadcast of Biret's first Moscow recital during her sixteen concert tour of the USSR in 1960 at the age of nineteen. The recording of Piano Sonata No. 2, the second recording of Sonata No. 7, both made direct-to-disc in 1977 at the RCA Studio in New York, and the Swiss, German, Turkish and Soviet radio recordings are all unedited single takes.