"The PMS was originally produced to encourage social singing of SCA-period music in my local area (Kingdom of Ealdormere)." So says Kirrily Robert/Katherine Rowberd in the introduction to her Period Music Songbook. There's a lot of Ravenscroft and other pieces that you're likely to have heard once or twice - she was aiming for a singable "top 40" collection of period music, mostly in English. I think she's hit her mark.
Those Ealdormerians! Always being so excellent in the bardic arts.