Capacitor dielectric type

I wonder if anyone can tell me what kind of capacitors are in the preamp section of my MusicMan HD-130 bass amp. They are yellow and have INDCO INT. printed on them.I mainly want to know if they are mylar.If so I will replace them with polyproplene.Would anyone have an answer? KMcC

Hi Kevin thay are Mallory-series 150 Metallized polyester .Some times thay say Plessey OR Westlake
Or Indco

Thanks Terry for the info,I guess I won't change them or maybe just the one's that couple the three stages, those I will use higher value polypropylene.Does this sound like a good thing to do? KMcC