Mack, I have heard that comment about C Melodies being out of tune before. The advice I have from the C Melody experts is that this is an undeserved reputation. They tell me it came about due to unmaintained instruments being dug out of attics and the back of grandads wardrobe after 40 or 50 years of being unplayed and unmaintained ........ its not therefore surprising that they were somewhat difficult to play tune!
A C melody should be no more likely out of tune with other instruments or itself than any other Sax of the same period if properly refurbished. The instrument were almost all craftsman manufactured by Beuscher, Martin, Conn or King. They made the best sax`s in the world at the time.
I recently loaned the best of my 3 sax`s to a professional Sax player who then sat in on a jazz session that we were attending along with two other good players on modern Sax`s. The sound he produced from my far from fully refurbished instrument just blew the other Saxes off the stage with its power, tone and presence. Yes, he used a modern mouthpiece (Most c mel players do) but it showed up the real quality and of these instruments for all to hear. And it was perfectly in tune as well.
I agree about the over heating Renault though........resemble a "bag of nails" don't they ;-).