On Comedy, Music and Retroactive Inevitability
Retroactive inevitability was a phrase used by the late Roger Payne, parody-writer extraordinaire, to describe that simultaneous sense of surprise and 'but of course'-ness you get when an end-rhyme forms a punchline.
You kind of know what's coming because of the structure that comes before, the length of phrase, the parallelisms formed by the rhyme scheme, and in the case of parodies also from your knowledge of the original song - though the structures need to make sense in their own right too. But the way the thought is completed is not entirely predictable, because the role of the comedy writer is to take us to places we hadn't necessarily thought to go.
So when the cadence-point comes, the moment of the 'reveal', it seems obvious - but only in retrospect.
This is a useful concept in stand-up comedy too, especially in conjunction with the concept of set-up and punchline as cliffs. If the joke is too obvious (cliffs too close together), people get to the punchline before you deliver it, so there's nothing to reveal when you get there. If the joke is too obscure (cliffs too far apart), you leave them behind. There is a sweet spot between obvious and obscure where the laughter happens, and this is a matter of both content and delivery.
(As an aside, as an audience member I quite like jokes where the punchline sits there like an unexploded bomb for a couple of beats before the laughter erupts. But these are scary to tell as you don't know during that moment of silence if the laughter is going to come or if it's going to just lie there like a dud.)
There is a knack to feeling out the pace of an audience, seeing how quickly they respond, and adjusting the trajectory from set-up to punchline to match them, so you can meet them there. This is a knack that I am still far from mastering - some days, with some audiences I can get it working like a dream and am convinced of my comedic genius, while other days everything feels like hard work. This of course is why performing is addictive.
In musical terms, I have previously likened this process to L.B. Meyer's implication-realisation model of musical meaning. Cadence points, climaxes, points of harmonic or melodic resolution all provide 'aha' moments, those moments when the musical thought is complete. Sometimes this is satisfyingly predictable, sometimes refreshingly surprising, but either way it needs a sense of coherence with what has gone before to elicit a meaningful response. A complete non-sequitur just produces bafflement.
At the same time, it needs some sense that that isn't the only possible way for the music to go, some sense that it is worth our while to listen and find out what is going to happen. 'I knew you were going to say that!' is only a matter of pleasure if seeing the prediction come true makes us feel clever or empathetic. If in fact that person never says anything else, we just tune out.
So retroactive inevitability is also part of musical meaning: the pleasure comes from the way it seems obvious in retrospect, but only in retrospect. And, like comedy, this is a matter of both content and delivery.
One of the differences between a communicative and a merely accurate performance comes from how these patterns of set-up and punchline, tension and release, are handled.
When people are well-rehearsed, they get very used to the patterns in a piece of music and start to take them for granted; they forget that some are more surprising than others, that there was a time when they didn't know how the phrase was going to end. I spend a considerable amount of time as a coach pointing out that a particular chord is not a given, but a specific choice; that the composer or arranger could have made other choices to different effects. The meaning of a chord lies in all the other chords that it is not. Singing a surprising chord as if it were perfectly ordinary just confuses the listener.
This is why techniques such as singing as if telling a story to a small child are effective. It's not just that people tend to exaggerate their expressive range in doing this (which is sometimes but not always needed). It's that they suddenly start thinking in terms of how to use the music to hold attention and interest instead of taking their listeners for granted.