"Duet' was recorded over three days in October 1978 at the Delphian School in Oregon. Corea stayed on a few days longer to record his next three solo albums: "Delphi" I, II, and III.
The Discogs entry for "Delphian Foundation" only lists three other recordings, all unreleased: a 1979 Corea/Gary Peacock duo; a 1979 Lee Konitz/Martial Solal duo; and an undated solo set by the pianist Mario Feninger.