What Plug-Ins did Toby Fox use for Undertale and Deltarune??

I really wanna know since I would love to make music with that specific instruments.

I only have Nes-VST and I need more.

I would also love to get Chapter 3/4 plugins since the music was indeed peak.

I hope you all can help me since I am a bit searching at the moment...

Can someone make a list?