(XML) what can i put in EngineSoundOverride?

i assume this can be used to change the engine sounds from the normal one to the more "meaty" sounds of larger rocket engines (this was mentioned in the update log)... so yeah, main question is, what are the usable options that i can put in the field?
(for those wondering, i need the SV80's engines to have a meaty but also deep screamy sound)