ROBERT SIEGEL, HOST:
Twenty-nine bars of music are making classical fans giddy today. Those bars make up a song called "The Heart of Man is Like a Mine."
AMY WILLIAMSON: (Singing in foreign language)
SIEGEL: It was written by composer Felix Mendelssohn.
MELISSA BLOCK, HOST:
Mendelssohn wrote the song in 1842, when he was 33 years old. It was a commission for an acquaintance.
ANASTASIA TSIOULCAS, BYLINE: He'd had no intention of publishing this or making it go public in any way.