Stravinsky in Rehearsal, from 1947:
In 1947, William Malloch, possessed by a sense of history, recorded Igor Stravinsky rehearsing his new revision of his Symphonies of Wind Instruments (in Memory of Debussy).
[In this 1961 program,] Malloch comments upon and plays this historical recording, which was broadcast by permission of the composer himself. The sound is antique but the picture of what Stravinsky is striving for musically comes through clearly enough.
An amazing find, it's especially interesting because Stravinsky is using the then-brand-new 1947 revision, which greatly clarified his intent in the piece. Listen here.