[MR] A period song and music source

[Tracie Brown]

Several, actually. All free. 
Steve Hendricks' (Master Samuel Piper's) collection. Hundreds of period instrumental and vocal works, including arrangements of all the Arbeau and Playford 1st edition dance tunes, madrigals, solo songs, many 4 and 5 part instrumental pieces from Praetorius, the Fitzwilliam Virginal Book, etc., etc. Invaluable and incomprehensibly underused.
http://sca.uwaterloo.ca/Hendricks/

The Werner Icking Music Archive. Not just early music, but a lot of it is. Searchable by composer and musical era. 
http://icking-music-archive.org/index.php

The Werner Icking Archive is also part of the International Music Score Library project (IMSLP) aka Petrucchi, which has even more early music. Thousands of pieces of free sheet music. 
http://imslp.org/

The Choral Public Domain Library, or, Choralwiki.  Yep, lots of choral and small group pieces. Many madrigals, many of which can also be sung as solos. Instrumentalists can play them too. 
http://www.choralwiki.org/wiki/

MusicaViva. Sheet music and more. Free, with higher quality prints for subscribers. 
http://musicaviva.com/

For traditional music, some of which is period, and somewhat more of which is period-appropriate (no train wrecks):

The Contemplator. Ballads and traditional songs with historical information. 
http://www.contemplator.com/

The Mudcat Cafe (Digital Tradition). Search both the DT and the forum, but be aware that not all comments are equally well informed. Verify. You'll generally need to find the tunes elsewhere. There are even some SCA songs in their collection.
http://www.mudcat.org/
One of the elsewheres for tunes is Yet Another Digital Tradition Page:
http://sniff.numachi.com/

Searches of John Chambers' ABC Tunefinder return traditional and some period tunes in several printable formats. Tens of thousands of them. 
http://trillian.mit.edu/~jc/cgi/abc/tunefind

These are just a few of the Internet sources of free, printable sheet music suitable for the SCA. Exploring them will lead you to others. Also. I recommend to everyone (and especially to performers of traditional music) to listen to live and recorded performances. Also, try learning it by ear and memorizing it. Traditional music is not meant to be performed with your eyes glued to sheet music! (Even if I do it myself sometimes ...)