Caption: A BBC documentary "Ludwig Koch and the Music of Nature"
Caption: A recording by Albert R. Brand in 1937 (Herringull, Canada), available at the Macaulay Library
Caption: A (focused) recording by Arthur A. Allen in 1947 (Gray-necked wood-rail, Panama), available at the Macaulay Library
Caption: A gramophone publication by the Cornell Lab of Ornithology "An Anthology of Over 200 American Bird Songs"
Caption: A gramophone publication by two of Peter Paul Kellogg?s disciplines, Jerry and Norma Stillwell, "Bird Songs of Dooryard, Field and Forest"