She worked closely with both teams while writing and changing melodies, and was in charge of the process. A few days later, Madonna posted an image of a sunset with the words "Rebel Heart" on them, and a caption which the media interpreted as lyrics from a new song. The lines posted were: "Day turns into night. I won't give up the fight. Don't want to get to the end of my days... saying I wasn't amazed." Additional images showed Madonna with singer Natalia Kills in front of a microphone, and with Martin Kierszenbaum, the founder and chairman of Cherrytree Records, and senior executive of A&R for Interscope Records, Madonna's label. By mid-April 2014, she had also revealed on Instagram the names of songwriters Toby Gad and Mozella and record producer Symbolyc One with images of the group working in studio. The list of personnel grew to include producer Ariel Rechtshaid and sound engineer Nick Rowe. In an interview with Sirius XM Radio, Kierszenbaum described the recording process:  We were supposed to be with her in the studio for a couple of days. She kindly invited us to stay a little longer. We don't know what's going to end up on the album but it was an absolute you know honor... For me being such a fan for so long it was so exciting to hear her vocal in the room right next to me, coming out of her head really sounding exactly like all those records we all love and she's a pleasure to work with because she's so in tune with who she is and what she wants to sing. I don't know. It's really great collaborating with her and Natalia is such a great writer. In May 2014, Madonna posted a selfie in which she talked about working with American DJ Diplo. She had invited him for her annual Oscar party, but he could not attend. They eventually started talking about music through texts and decided to collaborate on the album. Madonna asked him to provide his "craziest record" for the album. Together they wrote and recorded seven songs. "Those records are gonna be crazy-sounding. We really pushed the envelope with some of the stuff we were doing... [S]he was up for anything. I love when an artist gives a producer the confidence he needs to work with them, and Madonna was very open-minded to my ideas", Diplo added. One song was composed using a hook Madonna had sung in the studio; Diplo described it as "super weird".