The "legislation" is not clear since there is no definition of the word "public" in the 1988 Act. The quote from Emma B is, if my memory serves me, from PRS propaganda, and not from any legal source.

However, the courts have consistently been restrictive, and have consistently rejected arguments that assemblages are private rather than public. They often use the test of whether the occasion is "domestic or quasi-domestic".

Cases relating to performance only to workers, performances that are not audible to customers, are rarer. Distribution by Tannoy to workers only has been held public, and in a 1992 Australian case (based on identical principles) a performance by way of instruction to 11 bank workers in a single room to which no others were admitted was held public. Long ago, a play performance to doctors and nurses only at a hospital was held non-public, but that may be confined to its special facts. The Kwik-fit case was one in which customers and those near the premises, access to which was unrestricted, could hear the music, so it is not in point in this case.

I have not been able to trace any relevant case in which playing to a smaller number of workers was held "public".

I have no doubt that one worker listening on headphones would not be public. I can see no basis for saying that replay by a loudspeaker that could be heard by one person alone, and in circumstances where others could not come and listen, is public.

However, the PRS are often a bullying organisation, and I know that they have in the past used some lawyers (no names no pack drill) who are very keen on bullyboy tactics. By and large, if they are after you, you can pay up as demanded or be ready to go to the House of Lords.   

The MCPS may be a little more circumspect at times - perhaps because the Irish MCPS got (wrongly, in my view) a very expensive bloody nose in Ireland at the hands of the nightclub disco operators in the early 90s I think it was.

There can, I think, be little doubt that these restrictive interpretations of the law are out of public sympathy, but the chance of the law being put on a rational basis must be very slim.   To return to the PRS propaganda quote, I would submit that the public would accept the need for a PRS licence if the performance in question was used itself to generate, or with a view to generating, profit - eg to attract customers.   Likewise, arguably, if music is used in an internal (ie private, as most people would understand it) productivity scheme, a case can be made that the music is earning and so should be paid for. To go further than that is in my view not ""right" although the law may at present indeed go further than that.