As one of the most important aspects of a guitar, the bridge is a device that supports the strings on a guitar. It works by transmitting the vibration of the strings which in turn transfers the sound to the air so that you can hear when a guitar is played. Any instrument that is stringed produces their sound through energy to the strings which sets them into vibratory motion. However, the strings by themselves only produce a weak sound because they only send out a low volume as they vibrate. The strings need the ability for the sound to be transmitted to a larger surface area that then sounds the volume into the air which in turn produces louder sounds. A bridge is how this is done.
The positioning of the bridge is of the utmost importance. Typically it is placed perpendicular to the strings and larger surface. The tension of the strings pushes down on the bridge and therefore the larger surface underneath it. The surface is usually coupled to a sound chamber such as an enclosure like the body of the guitar. This works to assist in the sound amplification. The bridge can be made of wood as the top plate of the guitar or in other instruments it can be made of plastic, metal or even calfskin. Any material that vibrates with the strings can be used.
Bridges are usually made of a single piece of material that fits between the strings and the surface but in some cases the bridge can consist of multiple parts. One common bridge that can be found is one that incorporates a separate bearing surface which the strings rest on called a saddle. The saddle is usually made of a material harder than the bridge itself such as ivory, metal or bone. A classical style guitar uses a saddle that sits very loosely in the bridge and is only kept there by the tension in the strings. The saddle then has shallow grooves in it to prevent the treble strings from moving during playing.
Electric guitars in particular have two main groups of bridges. There is the tremolo and the non-tremolo, sometimes called the hardtail. The tremolo bridges have an arm sometimes called the whammy bar, which extends from below the securing point of the string. It works by acting as a lever that the player can pull or push to change up the tension in the strings which results in the changing of the pitch. The non-tremolo bridge supplies a secure point for the strings but don’t give any real control over the pitch or tension of the strings. There are a small group of tremolo bridges that have an extended tail which gives more reverb in the sound because of the string resonance found behind the bridge. Fender makes a guitar with this longtail called the Fender Jaguar.
All bridges have pros and cons, depending on who is playing it and what style they play, but in general the non-tremolo bridge provides the best tuning stability. It also gives solid contact between the body and strings making it one of the best bridges to have.