One of these was SCA’s concurrent growth with a revival in folk music, which began in the 1950s with musicians such as Leadbelly, Woody Guthrie, and Pete Seeger, and acquired mainstream acceptance in the 1960s with Joan Baez, Judy Collins, the New Christie Minstrels, and Peter Paul and Mary. Traditional songs and those with a similar feel received new popularity.
Another was our association with science fiction/fantasy literature, which also matured in the mid-twentieth century. One component of the conventions held by fans of this literature was folksinging, often late into the night. This was participatory music, with everyone singing along, especially when the words were printed up. The original lyrics might be sung, but a huge body of new words were written to the familiar melodies – words with science fiction or fantasy themes. Thanks to a typographical error, this came to be known as “filk” music. Since SCA developed from this culture, it continued the tradition of folk and filk singing in bardic circles. Many SCA performers have tried their hand at composing music, lyrics, or both. A few skilled singer-songwriters make their living with recordings and concerts of their music.
A third source for SCA music is the music performed during the SCA period. When SCA began, such music was primarily found buried in university libraries. A few madrigal groups sang late period music, but earlier music languished in academia. When the recording “Chant” was published in 1994, public interest in early music grew. Now there are many recordings of early music available, and some SCA musicians are playing and singing music that would have been heard in period, sometimes on home-made period-style instruments.
Different SCA kingdoms tend to have different musical/bardic cultures. Some prefer a performer/audience style; others prefer a singalong style, with improvised harmonies. Some prefer that non-period music be reserved for parties after the event. Northshield generally has a very accepting bardic culture. A timid four-year-old singing the ABC song will receive applause and encouragement as often as the semi-professional singing a period tune.
If you are looking for sheet music, one large source is the Pennsic Pile, which contains the sheet music that will be used for accompanying dancing at Pennsic.