Phil,

In the context of "Chanteys in the Royal Navy", I think it's quite clear that, in this article, Kate Jamieson is arguing that songs to accompany work (chanteys, shanties, or whatever label one attaches to them) weren't allowed, but musical accompaniment sometimes was.

Admittedly, her article doesn't quote sources, but she is contactable should you want clarification.

She certainly has a more lucid style than you.

Harry