I thought it was tested in a case involving kareoke.

This test was if a form of Kareoke was classed as 'recorded sound'. It was (eventually) found to be - on appeal.

One of the judges expressed their opinion that they considered that Paliament intended it to be - the same two individual performers - but this case did not decide the issue at hand.

It is difficult to see how it could be thought of decided - as the experts advise that there is no case-law that has determined what a 'performer' is.