A bridge is a brief section of a song that is different musically speaking, than any other section. It usually occurs just one time. A bridge lyric usually conveys new information, often with a different perspective.
Example: If the song prior to the bridge is about “why we can’t be together in a love relationship” the bridge might take the position “now if things were different in this specific way, then maybe our love relationship could happen.” Meanwhile the bridge music might differ– a different chord progression, a quarter note feel instead of eighth notes, etc. So in most cases, we’re looking for contrast both musically and lyrically, from the rest of the song.
That being said, sometimes the bridge simply drives home the point. It could have the same chords as the chorus and repeat a phrase from it. The idea is to hold the listener’s interest in whatever way best achieves that. What is the purpose of your bridge?
In my opinion, there are three main reasons to add a bridge:
1. The song is too short
2. The listener needs relief
3. To present new, contrasting, information in the lyric
If the song is under two minutes long adding a bridge to lengthen it might make sense. There are other options for lengthening, such as doubling the final chorus or adding a verse, so be sure a bridge is the best option.
Some songs reach a point where the listener is starting to lose interest. Inserting a bridge can be a powerful way to re-interest bored listeners and pull them back into the song. Once again, there are other options: A breakdown section or an instrumental solo are two examples. Experiment to be certain the bridge is the best choice.
If the song works well without a bridge, why add one? If your song is wordy, more words might even turn the listener off, a solo would almost surely be the better choice. .- b.e. watson