PHJim, there are similar patterns in the UK. Males tend to outnumber females when the instrument is the important thing, but females outnumber the males when it comes to singing either unaccompanied or with a (usually male) accompanist. Singer-guitarists are mostly male, and males outnumber females in most instrumental sessions, but females do at least as much or more of the singing in clubs and singarounds. Females far outnumber males in choirs of all sorts, including the many folkier "community choirs" that have spring up in recent years. I think that at most gigs and concerts, audience numbers are fairly balanced between the sexes.

I'm not attempting an explanation, just commenting on what I see.

Marje