So I was looking for a cheap tuner and ran into this (http://www.fender.com/accessories/fatfinger/).
Just clamp the Fatfinger™ sustain enhancer on to the headstock of any guitar or other stringed instrument. It adds mass to the weak end of the instrument, so strings ring out longer, louder, and with more balance. Dead spots can be tuned out simply by changing the point of contact to the headstock. The results are instant and impressive.
OK, from what I can surmise from there, they're saying if you add significant mass then less energy would be lost by the head vibrating, which I have no problem with in principle. But really, how much mass and what would the actual effect be?
Searching a bit found threads like this (http://www.harmonycentral.com/forum/forum/guitar/acapella-41/1116721-), where some are skeptical, but more are completely like "it's instantly noticeable, try it yourself", which I think we all here know where such statements usually lead. And then the "I was skeptical, but..." person shows up as well for good measure.
Then, reviews (http://www.musicianyou.com/articles/fender-fatfinger-product-review) that purport to do some testing, but it's not exactly what I would call "scientific".
So, what are your opinions? How plausible is this?
Generically it is very plausible. Adding weight to a vibrating structure is a standard mechanism for changing its resonant frequency, which will have the effect of enhancing its response to some frequencies and damping its response to others.
However, whether or not this specific solution will work as advertised is difficult to tell. You'd need to know some details about the stiffness of the guitar neck to work out how much mass you'd need to change its frequency response appreciably.
The whole point of a 'body' of a guitar (and all other stringed instruments) is resonance. Good bodies have long sustain for all frequencies. It's quite a difficult and complex thing to design well. To me this sounds like people who add a generic brand spoiler to their car. The thing is, spoilers are usually designed specifically for a car to improve fuel efficiency or traction (in the latter case it's usually called a wing though), and you have to get it exactly right. If you add something that isn't exactly right, the thing is making it worse.
Resonances in guitar bodies are extremely complex. I suspect the manual says something vague about that you should try to clamp it in different places and listen what works best (which gives big time expectation bias anyway), but I wonder whether it can make any difference. This thing doesn't add a lot of weight really.
Fender must have BIG PROBLEMS if they can't make a guitar with the right mass in the headstock! Maybe it makes it sound more like a Gibson?
I know guitar players often like to change the sound, but that's got to be a subtle effect compared using a different amp, swapping pickups, or using an effects pedal, etc.
So it's probably like I suspected. One of those pseudoscientific ideas based on a kernel of truth but completely distorted out of proportion by the practical application.
If you're going to add weight to the headstock, I doubt a little clamp like that would make much of a difference. If you added a significantly larger amount of weight, the balance of the guitar might become awkward.
As a bass player I can tell you that they can indeed be quite effective for dealing with dead spots on some (but not all) basses with this problem.
I don't know about the sustain bit. But one big question would be - if it does noticeably work, does it only work with some instruments?