The law is pretty clear that two musician playing in a pub is not a public entertainment and does not need a PEL.

In the above case the public certainly can in effect get in but it is clearly not considered a public entertainment.

It is not quite so clear that the addition of one more musician then automatically makes the event a public entertainment, without the further definitions of what a public entertainment consists of, being taken in to account.

Well not to me, but I am a musician not a lawer.