The original music was from Alias Conrad Coldwood. Many songs contained samples of questionable copyright and he was afraid that Content ID systems would copyright strike people he'd already given permission to use the music in the past. Here's a screenshot of his email and the source of it (from reddit sorry).
The music was pretty good so it's a shame, but I'm sure Toby Fox did a good job replacing it. Pepper Steak was the most well-known and was the regular battle music. It's swing (electroswing?) and very memorable. Also I really like Fake Orchestra and Minuit a fond la caisse.
Why do people keep saying this? I've lived nearby and known lots of 20 something mormons and none of them text or talk any different from the non mormons in the nearby areas (other than pronouncing milk as mɛlk and pillow as pɛlow)