Matthew Caulfield writes an interesting note in 150809 MMDigest
 [ http://www.mmdigest.com/Archives/Digests/201508/2015.08.09.01.html 
regarding this matter with ASCAP and asks some rather specific
questions which I cannot claim to answer.  However I have made
specific inquiries and gotten answers which may be helpful to some.

Our local AFM (musician's union) chapter recently hosted a seminar
at a local bookstore where the guest was Dick Weissman, author of
"Understanding the Music Business" and several other titles related
to the industry.  I frequently do performances singing to recordings
of piano rolls in public places for contributions made by audience
members, also known as "busking".  And if you happen to be in Eugene,
Oregon, on Friday or Saturday you can catch me at Blair Blvd. and
Monroe Street between 8 & 10 P.M.

I asked Mr. Weissman what the possibilities were I could get in
trouble.  He said, "None.  The performer is never the one responsible
for licensing.  That's the responsibility of the venue.  And when you
are performing on the street corner, no venue has been created."

If you want to know more you ought to get your hands on the book
mentioned above and check out Chapter 6, "Copyright and Performance
Rights".  There was also an article in the July 2015 issue of
"International Musician," the AFM publication, titled "Five Things You
Didn't Know about Performance Licensing" which might provide some quick
answers to common questions on the subject.  So there; hope that helps!

Lee Rothrock
Springfield, Oregon