There are basically seven major song sections that are being used today. These are the introduction, verse, pre-chorus, chorus, bridge, instrumental and outro. These sections clearly define the elements of song structure and form.
INTRODUCTION:
The opening section of a song. The introduction sets the state and enharmonic language of the song.
VERSE:
The primary function of the verse is to provide the information that will lead to the song's title. Characters and the story are introduced with the emotional tone. Each verse of a song typically has the same melody and/or music with new lyrics. Each verse is usually four to eight lines long, expressed to eight through sixteen musical bars.
PRE-CHORUS:
A short section that creates energy, or releases tension from the verse section connecting to the chorus. Usually a two or four line section, with a completely new rhythm to that of the verse and chorus.
CHORUS:
This is the meat of the song. Usually the most memorable melodic part of the song. The lyric here is usually reflective and emotional. The chorus usually has the section of the song often referred to as the "hook" (the catchiest, most memorable part of the song); the hook may contain the title. The title may also appear on first and last line. The lyric summarizes the idea and emotion of the song, which could be in general or very specific lyrics. The melody is usually the same each time.
BRIDGE:
This introduces a new section that may not be similar to either the verse or chorus sections. Most of the time the melodic range is similar of that to the chorus and may decrease or increase in intensity at the end connecting back to the chorus section. The bridge serves as a departure, or a release from the rest of the song; thus the bridge's purpose is to add more contrast or additional information to the song.
INSTRUMENTAL:
Instrumental sections are where one of the major instruments is played out loudly and sometimes with a bit of improvisation. The rest of the instruments usually support the major instrument (usually a guitar in pop and rock genres) while the singer rests and gets ready for the next section.
OUTRO:
This is the ending of the song; some songs end with the chorus repeating while the volume of the song decreases but today more than any other time, the outro is usually the ending section.
Once you have these sections planned out, you can basically focus on your creativity and improvisation of the instruments, lyrics, melody and harmony. Essentially a song is a blueprint with some sections already in place. With the song structure in place, you can focus your attention on creating originality and contrast.
