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.