Generally, the bridge is a part of eight or four bars leading the interest of the listener towards the most important moment of the tune that is the chorus.
Therefore, the bridge follows the verse and creates, generally, a harmonic and melodic tension towards the apotheosis of the chorus. With the exception of the verse and chorus, that are always present in a song, apart rare exceptions, the bridge is sometimes omitted. In rhythm and blues and form of pop music like soul, funky, jazz, disco and dance the bridge often is used.
Harmonic features of the bridge in a song
The bridge often has dissonant or suspended chords to create tension. With the term “suspended chords” I mean a chord in which lacks third, replaced with the fourth or a chord constituted from the superimposition of a fixed bass tone with different chords overhanging above it. This harmonic technique is called “Pedal”.
Example of bridge with pedal
Here is an example of a bridge of four measures with a pedal of a fixed dominant tone at the bass (the dominant is the fifth note of a key or scale). The fixed tone at the bass creates a harmonic tension and dissonance; this effect resolve on the chorus.
Example of a bridge with repeated chords
In this example there is a simple repetition of two chords (fourth and fifth degree) creating indecision and tension.
Other aspects of the bridge in pop songs
Also the melody creates a tension and launches the interest towards the melodic lines of the chorus. This often has notes of higher frequency regarding the verse and, therefore, the bridge represents the more effective and elegant way to go up the melody towards the notes of the chorus.
- The first two simple melodic fragments create a tension resolved by the scale launching the chorus.
The bridge, generally, has a full and dense orchestration; in other words, it has more instruments of the verse and has a more incisive character. Often, moreover, many arrangers, create one detach in the last one struck of bridge or the bridge. For example, different instruments accenting same beats.