not stupid at all. maggot therapy uses a similar technique as SUNSHOWERS--it plays sounds when they talk, at a rate of 1 sound per x characters. but it wildly varies the pitch beyond what is usually seen in games that use this technique--and uses sounds not normally used for that purpose. together, this creates the eerie reverberation...

so in gamemaker terms:
random_pitch = choose(-0.1,-0.2,-0.3,-0.4,-0.5,-0.6,-0.7,-0.8,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8) // every sound has a random pitch
audio_sound_pitch(our_sound, 1 + random_pitch); // we add it to the baseline pitch of 1, making it lower or higher
audio_play_sound(our_sound,0,0); // sound is played, and might overlap with the other sounds as this script repeatedly fires during dialog

in rpgmaker, it requires no code. just use one of several message plugins that play dialog sounds, like Yanfly's Extended Message Pack 1 for MV or KC_TextSounds for MZ, and make the pitch variance (and pan variance if desired) as big as you can, and disable sounds resetting after dialog.

basically, whatever you're working in, find a way to rapidly shift pitch, and use the right sound, and you're good! thanks for enjoying the voices, it was one of my favorite things :)