Karen and I have started working our way through the huge collection of old fiddle books in Glasgow University Library, and one of our earliest finds was John Clark’s Collection of New Strathspey Reels, published in 1795 by Anderson’s music shop in Perth. Clark’s family members, plenty of local people, and even the music shop itself have tunes dedicated to them, and there is a strict copyright warning on the titlepage: ‘NB. Such copies as are not signed & numbered by the Composers own hand write, are a Forgery & will be strictly Looked after.’
But what struck me was the number of reels that had almost identical, or completely identical basslines in the first strain: here are some examples (there are plenty more). click on the images to see them more clearly
The first two bars have 6 beats of the tonic I followed by 2 beats of the note a step above (or sometimes below) O, and the other two bars are a walking bass followed by a V-I perfect cadence. The third example shows some slight variation in bar 3, but only just.
In these and other examples the 6+2 of the first two bars remains even when it’s very clear that the harmonic structure outlined by the tune is 4+4 beats: the bass line isn’t under any obligation to follow the tune slavishly. Perhaps you know a session player who always starts off with the same chord patterns under every reel? This is clearly a practice with a heritage!