From what I understand, and granted that ain't much, the more mass at the headstock of an instrument the better it's resonant characteristics. Now, of course, folks are not going to rush right out and nail, glue or screw massive weights to the headstocks of their finely crafted instruments. There's balance to consider, and ease of handling the dern thing with such additions and don't forget, how are you gonna fit it back in it's case to transport it.
Perhaps Mr. Happy is referring to a harp guitar. A hundred years ago or so, a local instrument maker, Knutsen, became well known for his radical looking appendages that spanned from the upper bout of the bodies of ukes, mandolins, and guitars. These body additions were mostly hollow resonant chambers as the bodies were and almost always met at the headstock. Some had their own sound holes as well. In the case of the harp type instuments additional acoustic bass strings were added and therefore, where the two headstocks met there were also tuning pegs on the added appendage for the bass strings. Likewise, there was an additonal bridge to accommodate the other ends of the added strings. I should mention, not all of the instruments Mr. Knutsen made were of this harp variety. Some had the extended appendages but without any added strings, kind of a faux- harp instrument.
Perhaps it was a contemporary version of one of these that Mr. Happy saw. I've seen examples of these in a catalog. They're being made in Mexico. Some of the piuctures showed a guitar with not just one faux appendage but two extending from both sides of the upper bout and arching around to almost, but not quite, meet the headstock. Weird huh? Yep, those guy down there must be smokin' some whacky stuff. It looked like a guitar on acid. I also bumped into another contemporary local maker of harp guitars and mandolins. Some of his first attempts were rather crude, but no doubt, by now, his craftsmanship must be much better.
I don't know why someone would wish to resurrect the idea of playing such acoustic monstrosities, but I'm glad to know that someone has taken on the challenge of building them. These strangely misshapen harp instruments were, no doubt, early attempts to create additional cousins to the stringed instrument family that could do more than just play within their given tonal range. Perhaps the faux harp examples by Knutsen were experimenting with the possibilities of increasing the volume output. Who can say for certain?
I own a Knutsen lap guitar. The body's upper bout tapers to the width of the neck of this guitar and ends at about the fifth fret. Again, this seems to be an example of Knutsen trying to capture more of the resonant qualities of the more massive neck. The sound quality produced by this design has a beautiful resonance. I suppose that part of the reason for it's wonerful tone could be that it is set up as a lap style guitar. With higher action because of the raised nut there's more tension on the strings and therefore more vibration being applied to the top. Or perhaps even it's age may play a role.