I also saw some other melodies, namely
-Sweet Capn Cakes part 1 in Castle Funk https://undertale.wiki/d/t/possible-sweet-capn-cakes-leitmotif-in-castle-funk/5457/15
The 1st 8 notes are of the (i think) 1st phrase of the part 1, just that the purple note is pitched down 2 semitones more than it should be, and then from the purple note until the last note in the screenshot it's the same melody at the end of the Part 1 of Sweet Capn Cakes (this part was the one i delved into on the post i linked)
So TL;DR, it might be a fusion of both phrases of the motif with some changes
Not sure if this is enough, but to be fair it does make sense since this song plays when K_K starts performing in the Café
-The other is Dark Truth in 2nd Sanctuary, I haven't made a video or post yet but to explain it I think the 1st half of Dark Truth is in 2nd Sanctuary, which i think would also make sense given that there's a song that plays in an area in the 2nd sanctuary which is Dark Place reversed and chopped up