Understanding why most guitars constantly go out of tune?

A guitarist with an engineering point of view:

This has been going on since they first started making guitars and all stringed instruments. If we think of any stringed instrument as to having a setup very similar to the Golden Gate bridge. The wires are anchored at each end and they travel over two bridge towers.

On a guitar, the first bridge tower at the tail end of the guitar is called a BRIDGE or on some guitars a saddle. The other bridge at the head of the guitar is called the NUT.

Now here in lies the major difference between the bridge and the nut of a guitar.

The bridge on most guitars tilt or move ever so slightly when you play with the strings. This very small movement prevents the strings from binding due to the friction between the strings and the bridge however that is not the case with the nut. The nut on all guitars do not give, bend or move. The nut is extremely rigid and immovable microscopically.

This rigidity is the primary reason that when strings must move by fractions of a hair when playing that they do not return to where they were when properly tuned. The FRICTION between the string and the nut is what causes the string to not be able to return to where they were properly tuned.

We have designed and developed two methods of solving the problems that are associated with the nut of all guitars. We can either prevent the strings to move at the nut or we can allow the strings to move more freely at the nut.

#1 The String Lock prevents the strings from moving.

( This method absolutely needs a Fine Tuner behind the bridge or saddle )

#2 The String Release allows the strings to move more freely.

( This method was designed primarely for acoustic guitars with three tuners on each side )