The use of a mysterious song as a plot point in Star Trek: Discovery season 3 has echoes of a divisive plot point from the Battlestar Galactica season 3 finale, which also centered around a piece of music that had found its way into the minds of different characters
Star Trek: Discovery's season 3 episode "Forget Me Not" introduced a piece of music played by Gray (Ian Alexander), the previous host to the Trill symbiont currently residing in the human host Adira (Blu del Blasio). While this song was written specifically for the series, a seemingly innocuous piece of music becoming a major plot point is reminiscent of the Battlestar Galactica season 3 episode "Crossroads, Part II," which used an arrangement of "All Along the Watchtower" to lead its characters into a shocking revelation.
Adira is still mourning Gray, who was their boyfriend, and maintains a connection with him and Tal's other past hosts by continuing to play the cello. It's not unusual for Adira to remember the song they heard Gray playing on the cello, and to play it themselves, given that symbionts pass on both skills and knowledge from host to host. What was unusual was that the same piece was also being hummed by the Barzan family (shown in recordings) on the seed ship in the following episode, "Die Trying." The mystery of this music continued when Michael Burnham learned that the tune is widely known among the remaining Federation citizens, though no one knows where it came from or what it's called.
Similarly, "All Along the Watchtower" was being hummed by several members of the Battlestar Galactica company in "Crossroads, Part II." But while the song in the older sci-fi show also has an unknown origin, the details are different. In Battlestar Galactica, the song is being heard by only four people, including Colonel Tigh, a forty-year veteran of the military. It is ultimately revealed by the end of the episode that the music is a trigger – a virtual "switch" that flips on to wake up the Cylon personae of four key characters. In Star Trek: Discovery, Adira and Stamets eventually figure out that the music is a distress signal being sent by a starship stuck inside a nebula. When the distress signal's source is investigated in the episode "Su'kal," the truth about why the music originated at the same time as the Burn is also revealed.
Battlestar Galactica's use of Bob Dylan's song, which was arranged and performed for the show by Bear McCreary, was divisive among fans because it was disseminated via some cosmic connection the Cylons shared. It also caused contention because it cemented the show's setting as being sometime after the 1960s. Before the identification of that song, the time period for the show had been somewhat nebulous and could have been in Earth's past or future.
Star Trek: Discovery's use of music with a sci-fi twist was less contentious, but the truth behind it was also more anticlimactic. Rather than being a season-ending revelation, the source of the song moved the season 3 arc forward; however, it effectively just served as a set of coordinates to guide the Discovery's crew towards the source of the Burn. Battlestar Galactica's use of "All Along the Watchtower" may have been more controversial, but it was also far more memorable.