Two of the songs on the soundtrack, "Go Now" and "Don't Go Down", are written by Glen Hansard, the Dublin native artist who won an Oscar for his song "Falling Slowly", featured on "Once", another John Carney movie.
When Conor first goes to Eamon's home at night to create a song with him, he has three LPs with him. Conor and Eamon play tracks from two of them ("Steppin' Out" by Joe Jackson, and "A Town Called Malice" by The Jam), but not from the third LP. That third LP, which can be partially seen on the room's floor: "Regatta De Blanc", by The Police.
While there are similarities to The Commitments (1991) (including the casting of Maria Doyle Kennedy), director John Carney has explicitly stated in an interview with The Verge that no homage to that film was intended. He also debunked the notion that the use of rabbits in Sing Street is a reference to the character Jimmy Rabbitte in the earlier film. Rather, it was a characteristic of the real-life "Eamon" that he knew as a teenager.
Although it was announced in 2014 that U2's Bono and The Edge were working with John Carney on this film, the collaboration did not come to fruition, except some back and forth in the development stage, due to scheduling conflicts.
During Conor's discussion with Brother Baxter about his use of makeup, Baxter claims that, if Conor is Mozart, that would make Baxter Salieri. Antonio Salieri was an Italian-born composer, contemporary of Mozart, and generally thought to have been one of his biggest rivals and competitors, using his position in the court of the Holy Roman Emperor to secure prominent jobs and staging for his work, while blocking the development of Mozart's career.
The usual disclaimer about characters and events is modified like so: ""Whilst parts of the film may be inspired by real life events, the characters, organisations and events portrayed in the film are entirely fictitious. Any resemblance between them and any actual individuals, businesses or events is coincidental, not intended and should not be inferred."
The fictionalised period version of the Synge St CBS (Christian Brothers School) was shot in the real, and still existing, Synge Street CBS school buildings, on Synge Street, in Dublin 6, in Ireland, hence the slightly odd disclaimer re the school itself, in the end credits.
The trivia items below may give away important plot points.
John Carney on the ending: "Well, I don't see it just as a happy romantic ending. I think that's the tone of the piece, but I think it's more like... they're setting off together, that's true, but I wouldn't say that's some huge relationship that's going to last forever. They're kids. I sort of hope the scene at the end would look a little like a fantasy sequence. You're supposed to wonder where the reality ends and the pop video begins. But people are actually taking it very seriously, and people are presuming it's fully real, which is interesting. That wasn't the intention."
The end dedication "For brothers everywhere" is presumably intended to reference the brother siblings and/or brotherly love, but the brothers could also refer to Brothers, as in the name pre-fix for Christian Brothers religious order members. This alternate now gives a different meaning in light of the action of a certain Christian Brother.