Lady Gaga's long-time collaborator and producer Madeon revealed some details on how he ended up producing 911 for Chromatica.
The song already existed, with a rough production from Bloodpop and co-written by Justin Tranter I believe.— Madeon (@madeon) May 25, 2022
I heard a demo and really loved it ! At first I suggested people I thought would sound good working on the production but eventually Bloodpop invited me directly.
Madeon shared on Twitter that he was called by BloodPop, and that the song already existed, but he added his own input into Chromatica, more precisely, he wrote and produced "911" along with Gaga, BloodPop, and Justin Trenter. Madeon explained that he hadn't seen Gaga in years, prior to "Chromatica" sessions, and that she was kind to him and how they danced together to "Rain On Me" demo. He tweeted:
The song already existed, raw produced by BloodPop and co-written with Justin Tranter, I believe. I listened to the demo and loved it right away! At first I suggested some people to produce the track, but I ended up being invited directly by BloodPop. I worked from home and redid the drums and bass and other details. Afterwards, I went into the studio with them and tweaked the chorus a little bit + wrote new chords, but the soul of the track was already there before I arrived! It was wonderful when Gaga recorded the final vocals. I hadn't seen her in years and she was as sweet and graceful as ever. In fact, one of my favorite artists. We ended the day dancing together to the Rain On Me demo - a very special moment. I have to mention Rami Yacoub who was there and delivered great ideas too.
Madeon is a French DJ and music producer, he opened for Gaga on her Born This Way Ball Tour and also worked with her on ARTPOP, writing and producing Venus, Marry Jane Holland, and Gypsy.