Joanna was a piece of piano music that was composed for Joanna Mills prior to the year 1840. Only two physical copies of the sheet music existed; one owned by Joanna herself, and the other by the original Quentin Collins. The song came to represent Joanna Mills for Quentin, with whom he was involved in an extramarital affair.
After her death, Joanna Mills' copy of the sheet music came into the possession of Samantha Collins, who used it in her plan to make Quentin believe that Joanna had come back from the dead.
- Although it is not stated on the series, it is implied that either Quentin Collins or Joanna Mills composed the music, thus explaining the existence of only two written copies. In real life, "Joanna" was composed by Robert Cobert, the primary Dark Shadows music composer.
- Various recordings of "Joanna" exist, including the original piano recording and a more elaborate piano version, as well as piano/harmonica/acoustic guitar, solo harmonica, and solo acoustic guitar versions as the love theme from the film Night of Dark Shadows. These recordings can be found on the albums Original Music From Dark Shadows (Volume 2), Dark Shadows 30th Anniversary Collection, The Complete Dark Shadows Soundtrack Music Collection and the House of Dark Shadows / Night of Dark Shadows Original Motion Picture Soundtrack.
- "Joanna" and its variations are known as cues 323-326, 328-329, and 331 in the original archives of Dark Shadows music. These cues do not include the versions created for "Night of Dark Shadows".