Paul Klein:

We stripped back “ILYSB” in 2015 for a performance at the Snapchat offices in Venice, and nothing’s really been the same since. people have become obsessed with hearing our songs presented in a more minimalistic way, and I think that’s actually really nice and quite the compliment. I was classically trained in piano for 13 years growing up. after spending probably 20,000 hours on a piano bench, I’d like to think there’s something special about the energy that exists between just me and those 88 keys.

—via FAULT Magazine

Paul Klein, the lead singer and song writer, talked about it in an interview.

Klein was in the car with a woman who was on the phone with her sister. She ended the call by saying “I love you so bad” and Klein instantly loved the phrase, telling her that night that he wanted to write a song with that title. From then on, the two would send each other texts saying “ILYSB” and a few months later it became a song.

Another tidbit Klein mentioned is that the woman had written “ILYSB” on a sticky note in his car and that he still had it at the time of the interview (April 2017).