There was a period of time when Lana and Barrie would just... travel, everywhere. I think they would visit random studios writing/recording songs there with whoever was available. It's hard to pinpoint what was made by who beyond them 2. I think they would sometimes just leave the songs in the studio even. UFB was never planned to be included on UV, they just made it for fun, they were in love. Whoever was the working engineer in the NightBird studios the day they recorded it is probably the son