Good question! Though, what different people consider similar to SGaP is going to be subject to some amount of opinion and personal preference. All I can offer is my take, but I invite others to pitch in with anything they’ve found

Popular opinion holds that SGaP’s early style (The Standard Model) is quite similar to that of Pogo (aka Nick Bertke), take Alice for (a fourteen-million-times overused) example. Generally speaking, the genre of music which employs splicing of vocal clips to create breathy atmospheric music is known as “plunderphonics”, so if that’s what you’re looking for then there’s the closest word to describe it. I quickly typed it into Pandora and got mixed results. The actual band, Plunderphonics, wasn’t to my liking, but Christopher Willits and his album Surf Boundaries seemed to show great promise, imo

What SGaP eventually evolved into is a lot harder to qualify. Personally I only know one other artist doing anything like it. cubesato (aka Satoshi Yoshitake) and their track ZOOO could easily be mistaken for actual SGaP. You ever see that PMV Dork? Again, music by cubesato. Blows me away. Shame so much of their work seems to be tied up in commercial branding. Then again, that’s what happened to Pogo as well

So this is what I have. Not a lot. Who else knows artists (preferably outside the MLP fandom) similar to SGaP?