A basic oldschool organ going through a bunch of cheap analogue gear?
Just layer some sinewaves at different octaves and add a bunch of stages of subtle saturation.
a good old organ sound, possibly a B3 or one of the many Farfisa's out of Italy
several ways to emulate this but try to find an organ vst is your best bet
for me this sound is built of 8' + 4' +2 2/3'+2'+1 1/3' + 1' sine waves e.g. root + octave + 12th + double octave + 19th + triple octave: the mix is the key to getting this sound so using a vst is a better route to getting the sound