A song is a set of lyrics put to music, meant to be sung or rapped. It has to make a listener stop what they’re doing and pay attention, then react in some way (cry, dance, tap their feet, buy the song).
Musicians write songs to express themselves, to entertain others or even to tell stories. They can be simple or complex, and can feature one or many singers. Some songs are a cappella, without any instrumental accompaniment. Others can have a solo singer supported by an acoustic guitar, keyboardist or pianist, a duo, trio or more. In classical music, a song can also be an aria or recitative.
Some songs are part of a culture, such as lullabies, folk songs and ceremonial songs. They can accompany dance, work or religious ceremonies. Other folk songs tell stories, such as ballads and narrative lyrics. Some are about specific events, such as a tragic incident or love story, while others are sentimental or sentimentalised.
Other songs are more commercial, such as torch songs, novelty songs and anthems. Pop and rock music are the most common commercial genres, but there is also a wide range of other kinds of music including classical, jazz, country and blues. There are also a number of specialised genres like country gospel and choral singing. Songwriters often use structure as a guideline, but it can come down to a lot of trial and error when working out the best arrangement for a particular song.