There's a great set of soundfonts of these machines floating around, Optigan, Orchestron, Birotron, Chamberlain... Popol Vuh used something like this (might've

There's a great set of soundfonts of these machines floating around, Optigan, Orchestron, Birotron, Chamberlain... Popol Vuh used something like this (might've been a prototype or something from what I've read) for example on the Aguirre soundtrack.