Mouth Music

5 of the tracks posted are examples of mouth music; the exception is "Fionnaghuala", which is often mistaken for mouth music (even though I have never heard an instrumental version of this song).

My theory is that it is a comical song based on intoning or incantation; something that might have been sung to entice the fish. In this case, the 'fish' are probably a euphemism for something else.