It's a pretty lengthy document, and in an unwieldy format that makes it hard to search, There is a section headed "Spontaneous singing. music and dancing"- but I couldn't find any definition of "spontaneous". Perhaps it's somewhere else in the 199 page document.

The nearest that paragraph comes to an implied definition is "In the case of genuinely spontaneous music (including singing) and dancing, the place where the entertainment takes place will not have been made available to those taking part for this purpose". Which leaves it wide open, but doesn't seem to insist on it being spur of the moment.

But it's bloody comnfusing. What does "been made available" mean? Would "Is it all right if we play in here on Tuesday?" followed by a "Yes" count as "made available"? And what is the implication of the word "entertainment" here? Presumably this has to mean something over and above people merely making music for their own enjoyment. And that goes against the "spur-of-the-moment" interpretation of "spontaneous".