A song is a musical piece utilising a person's voice. It contains words (lyrics) and have been known for thousands of years.
Many medieval songs are religious in nature or equally they might have been designed to be heard by the general populace. Some of them have a decidedly adult content and many can be very humourous.
Much surviving music for songs is religious and some may be quite complicated.
Song in Recreationist Groups
Songs in recreationist groups can be varied from historical songs being sung accompanied by recreated historical musical instruments, to modern songs with the lyrics altered (aka filk).