Legal requirements for mucians

Hi can anyone tell me what paperwork is required for solo/duo's musicians to work in bars.

I used to play regularly in a bars 20 years ago. At that time work permits for musicians were not needed as it was considered that musicians were not taking work away from the Spanish, and the local and civil police used to come into the bar, but never once asked to see any paperwork. Is this still the case?

I'm only intending to do this as and when I come on holiday, as a few bar owners that I know have expressed an interest in myself and/or a friend of mine playing in their bars.

If and when I eventually retire to spain I would probably do it on a more regular basis

If theres any musicians out here who could give me some guidance it would be much appreciated

Phil