I just came across a site showing some listings from Wagstaff's new catalogue of rare old books, for 1780. Amongst the books listed there is one called "Knibbs Dissenting Psalm Tunes Set to Music". It was on sale for 1 shilling and 6 pence. It was also listed in the next years catalogue so either there were lots of them around or no-one bought it the first time round. Don