I was hoping for some help with an R.A. Moog Melodie Theremin that I was just given.

The construction manual is a scan of what came with my Melodia.  As far as I know all the Moog produced instruments were positive ground, as Dewster has figured out for your instrument.  Around 1961 Moog published an article about a transistorized theremin which was the same as the Melodia, but it used NPN transistors and had a negative ground.  I don't know why there was a difference.  Supposedly PNP's were less expensive and if so that might give a kit from Moog a slight price advantage over doing it totally yourself.

Originally the instrument used a holder for a 6 volt battery, but that battery is no longer available.  The 4 AA cell holder shown in the picture is what I installed in my Melodia.  It looks very similar to the original holder.  A black plastic battery holder would work fine but would look less authentic.  If you happen to install the batteries backward the melodia will not work but it doesn't seem to hurt it. (Ask me how I know!)

The large hole on the right is where the pitch rod goes.  If you do not have that I can give you the dimensions of mine.  The two small holes in the center of the lid were added later but why is unknown.  Perhaps a music holder was attached there? Yours has the old logo on the front panel, so it was made before 1964.

The Melodia has a nice sound and I think you will enjoy playing it.  I started with an inexpensive 15 watt keyboard amp and it sounded OK, but when I got a larger amp it really sounded sweet.  There are videos of Rob Schwimmer playing a melodia if you want to see what it sounds like.

"Around 1961 Moog published an article about a transistorized theremin which was the same as the Melodia, but it used NPN transistors and had a negative ground.  I don't know why there was a difference."  - senior_falcon

The shift from germanium as a semiconductor to silicon was right around then.  Moog was probably just following the general industrial trend.

I think that both the NPN and PNP transistors in this design were germanium.

"I think that both the NPN and PNP transistors in this design were germanium."  - senior_falcon

Hmm, that would be sort of strange, as NPN germaniums are fairly rare and were more difficult to manufacture.  Rather like the silicon PNP and PJFET - you only really use them for push-pull or other specialized needs.

"A Transistorized Theremin" by Bob Moog in "Electronics World", 1961 shows NPN transistors, either 2N168A or 2N1086 both of which are germanium. 

No idea why the published theremin would differ from what he was producing himself, but he was trying to sell theremins and theremin kits and as I speculated earlier, maybe that would have given a slight price advantage to his own products.

Interesting.  Transistors were fairly expensive back then (designers had to take great pains to minimize the count) so that would be one way to sneakily differentiate product vs. DIY costs.