We all know that with an acoustic guitar the wood and the body of the guitar are crucial for the sound, but is that also the case for an electric guitar? In the video you hear how a music box, which makes vibrations like a guitar string, gets louder when connected to a solid wooden surface. This is because the larger surface area can better transfer* the energy from the vibrating music box to the air. The type of material (type of wood, stone, …) obviously plays an important role in the energy transfer, but discussing these differences would go beyond this article.
The solid body of an electric guitar in comparison with a hollow body still helps the energy transfer of vibrating strings to air a lot, but that is not what an electric guitar is designed for! An electric guitar gets amplified electrically, so we are not interested in its energy transfer to the air. The body of an electric guitar helps to sustain the energy of the vibrating string! We want to conserve the vibrational energy of the string within the guitar, so that the pickups have a good vibration to ‘pick-up’ electromagnetically. This is the reason why solid body guitars sustain longer than hollow body’s: a hollow body transfers more energy to the air than a solid body, which causes the string to die out quicker.
Not only is the body of your guitar important, but the bridge and nut that connect the strings with the body of your guitar are of equal importance. If the suspension of your guitar strings is solid and forms a good connection** with the body of your guitar, then the better the vibrations in the string can develop and sustain. This entire system forms the foundation for the sound of your guitar!
Guitar pickups translate the vibrations of the guitar strings into an electrical signal and shape the signal along the way, but if the vibrations of the strings are undesirable to begin with then there is very little a pickup can do to improve the sound. I.e. putting great pickups in a cheap guitar is the same as giving a great guitar to a bad player… The sound won’t improve much 😊
So if your guitar lacks sustain or the overall sound is not pleasant, then it is a good idea to inspect your guitar strings and their suspension (bridge, nut and the guitar body).
*Note that there is no amplification. What actually happens is a better acoustic impedance matching, which results in a much better transfer of energy from one medium (mechanical strings) to another (wood and/or air).
**In the video you can also see that if we just lightly touch the table with the music box, the sound still gets louder but not as loud as with a proper full connection.