finding early tunes sheet music

I find some good Renaissance tunes for my pennywhistle sometimes by looking online for sheet music intended for recorder players. The sheet music for recorders is often already shown in just a single melody line, which makes it an easier transistion to whistle melody.  In contrast, sheet music for voice, guitar, keyboard etc, has multiple parts or stacked chords, making it hard to pick out the simple melody for a whistle to play.