In an interview with Puissance Nintendo, Abby Trott – the English singer behind Super Smash Bros. Ultimate’s Lifelight theme – said she cried when she found out what game she had been singing for. She considers herself a “life-long fan of Nintendo,” so being involved with Super Smash Bros. Ultimate was a “really special” experience for her. Trott said:
“I was lucky enough to have the opportunity to audition through Cup of Tea Productions, and at the time I had no idea what the audition was for. For the first round, I submitted my singing demo. The second round involved singing a requested song (not ‘Lifelight’). I ended up being cast, and CRIED when I found out what the project was. As a life-long fan of Nintendo, being a part of Smash Bros. Ultimate is really special to me. I love ‘Lifelight’ so much.” In the same interview, Trott also stated she she “spent a day in the studio working out our approach and recording everything” with others involved.
Source: Nintendo Everything