The recorders were used in the 1950s and 1960s in the Schola Cantorum Basiliensis.
As baroque instruments are mainly tuned at a'= 415 Hz (unlike the present day standard of a'= 440 Hz), pitches notated as c2, g1, f1, c1 and f sound a semitone lower on these historic instruments:
b1, f1 sharp, e1, b and e.