Sorry Tom I can't find them either.

Bob, I believe you're asking for documented sources that you can site, that tell of a process of someone learning shanties, yes?
I'll go over some books but off hand I believe there references to examples in "On Board the Rocket" I'll check around anyway.

While being the honorary shantyman (1978 or 9) on board the museum brig Cathaginian at Lahinia I met George Herbert (the "Master Rigger from Geelong", as I later can to know him as). He started out as a cabin boy in the Baltic trades around 1912 or 14 at age 12 or 13, he later ended up in the Cape Horn trade before promising his bride to be that he'd swallow the anchor in Aust., he then began his trade as a rigger (his work is to be seen on the Elma Dopa, the Golden Plover, the Endevour-as a consultant, the Hawaiian Chieftian, etc.). I don't know if he sang on board as a shantyman but he told me that he did start to collect the from his early days. He played alto uke, concertina (english I think from the sounds of the tapes he sent me, I never bothered to look when I was with him) & harmonica while at sea but I don't know when this started. I believe that a couple of the songs that I have from him came out of his early days in the Baltics. The "Albertina" & the "Good Ol Brig" both found in Hugill & a few other places but not George's versions. So These he would have picked up as a youngster while in the trade & kept them in his repertoire for later use (use for what, I'm not sure but he could sure sing them in him late years). Anyway if it's printed sources you seek, I'll look as I do remember reading something to state that but where, I'll have to look.
Good luck

Barry