Guitar pitch changes with pressure applied to neck

Question

I have an Epiphone Les Paul Standard PlusTop Pro I purchased in 2016. I think it has a glued in neck as opposed to a bolt-on but is not a guitar made from a single piece of wood.

Whenever I'm tuning the guitar and put pressure on the neck the tuning changes with it.

If I push the guitar neck towards me and pluck a string, the tuning meter will tell me the note is sharper proportional to the amount of pressure I put. If I pull the guitar neck and pluck a string, the tuning meter will turn proportionately flatter. The change in pitch is more than a few cents. I'm guessing the pitch also changes when I hold down frets.

Ideally, the pitch should stay the same even if there is pressure applied to the neck. When looking for a new guitar, are there factors which predict the guitars that are less likely to do this? I guess one tell-tale sign would be whether the guitar is made from a single piece of wood. Are there any others, let alone going in to the store and trying it out? May be the kind of wood use for the body?

For my guitar I did put in a lighter set of strings so the truss rod may need to be adjusted.

I found these related articles:

Electric guitar tuning changes in different holding positions

Putting (almost any) pressure on guitar neck warps sound

Answer 1

'Ideally the pitch should stay the same' - true, but there's rarely an ideal in this world.

You're talking about a thin piece of wood, supported inside with a thin steel trussrod, being pulled like a bow by six steel strings, trying to bend it. In balance - as it is when not being purposely pushed and pulled, it does a great job. It's static, and there's no great force moving it.

But, that force will affect it, whether it's helping the string tension by pushing forwards, or aiding the trussrod by pulling backwards, so the balance is unstabilised. That's the nature of the physics.

There was one manufacturer - John Birch, who would place his guitar between two chairs, and stand on it. It never broke, but I dare say the strings went out of tune!

So, unless I've missed the point of the question, You'll probably never find a guitar that doesn't respond to tension changes to the neck - unless you have tens of thousands to spend - and if that's all that worries you, maybe guitar isn't the right instrument !

Incidentally, there are few guitars made entirely from one solid piece of wood. Yours has a set neck - fitted into a perfectly shaped pocket, and glued. Some say that's better for its sound, than those which have the same sort of pocket, but screws to join the two together. If you break your neck, it's a new guitar needed - so, please, stop trying to!!

Answer 2

I don't know how much pressure is getting what response, but pushing and pulling the neck to get whammy bar effects on hardtail instruments is a common thing. I mean, pulling would tend to just get fret buzz, so that's less common, but it is a technique. Jake E. Lee did the dive bomb on Ozzy's "Bark at the Moon" with the tuner, but it's the kind of thing you can do with a neck bend. Slash broke the headstick off a favored Les Paul doing just that. So, be careful and don't overdo it.

I mean, I can't say there's no problem without more info — like having me hold and play it — but it didn't sound like a problem.

Answer 3

Some guitars are inherently more flexible than others, and therefore the tuning becomes more variable depending on the various pushes and pulls exerted by the player and by the force of gravity.

One thing that might help in your case is to check your truss rod and perhaps tighten it slightly. All other things being the same, a tighter truss rod makes the neck more rigid and therefore less prone to detuning when pushed or pulled.

Whether the guitar is made of a single piece of wood is not necessarily an important factor. Much more important is the inherent rigidity or elasticity of the wood used for the neck. That's where 99% of the detuning will come from. Detuning from body elasticity will usually be negligible.

The only thing one can do with a bolted neck is to make sure that it's attached properly, in which case it'll not cause detuning. Again, that's virtually all from the neck, and besides making sure the truss rod isn't unnecessarily loose, there isn't much else that you can do.