Hahahaha...I'm sorry but I just had to laugh........You may be very correct in your suggestion as to who the 'Mermen' are that are on his tape....But....I would venture to guess (pun fully intended and will hopefully make sense in a moment......DING! ;-) that the instrumental 'Mermen' group he is referring to is actually the 90's intense surf band from SF called 'The Mermen'......Not surf music as in The Beach Boys, but along the wave of Dick Dale, et al....
Hope that helps....Cheers!! They are a great band by the way; and REALLY REALLY f*ing loud live...a tad too loud if you ask me, but only for the venue in which I saw them I guess... Hope y'all are well... Peas.....Sir Lance