Yes, perry comes from pears now, and cider comes from apples,
An obvious distinction with which every brewer grapples.
The "hook" line at the end of each chorus is "cider comes from apples, and perry comes from pears", but (employing a fairly common comedy technique) the wording is changed at the beginning of each chorus so that a different rhyming word comes last. I'd already had "perry" and "cider" at the end, so now it was the turn of "apples". Getting "apples" to the end was no problem, apart from a minor problem with the scansion - "pears" is only one syllable, so I added in the "now" as a filler. Not ideal but good enough. The second line was a lot harder though.
The first problem was finding a rhyme for "apples", which has far fewer rhymes than the other words. Off the top of my head I could only think of "dapples", which didn't really fit the context, and "grapples". Something like "a problem with which [someone-or-other] grapples"? That seemed promising - in conversation you'd be more likely to say "a problem which [someone-or-other] grapples with", but the other version is perfectly grammatical and the slightly pedantic tone may even enhance the humour. So that was a start.
So who's this person grappling with the problem? No idea. It's really a problem with which lots of people grapple, but then you need the plural version of the verb "grapple", which doesn't rhyme. What about "everybody", though? That refers to lots of people, but takes a singular verb. Now I've got "a problem with which everybody grapples". Scans OK but is two beats short. Stick in an adverb and adjective, then, and here's the first draft:
A really tricky problem with which everybody grapples.
It's not really a problem, though - it's a difference that people don't observe. I'd already used "difference" in a previous chorus so I needed a synonym. "Distinction" fitted, but then the adjective needed to be shorter:
A really clear distinction with which everybody grapples.
OK but I thought I could do better - "really" is a bit of an over-used filler word and I'd rather do without it. Is there a synonym for "clear" with three syllables that fits? Indeed there is - "obvious":
An obvious distinction with which everybody grapples.
Nearly there now, but does everybody grapple with it? It's only really the people in the brewing industry who name the product - that's who the song is trying to make fun of. So the line now becomes:
An obvious distinction with which every brewer grapples.
And I went with that, but actually it's still not right. You don't brew cider, you ferment it. But "fermenter" doesn't scan, and anyway I don't think people who make cider are called "fermenters" - just "cider-makers". But then I'd have had to repeat "cider" in the line, and rewrite the whole thing again because the scansion would be different. I just had to hope that no one would notice.
In performance it's just a little throwaway gag that hopefully gets a titter from one or two people in the audience. But it represents something like an hour's work, I'd guess. I'm not saying that every line in the song was as hard to write as that one, but it gives an indication of the type of work that goes into writing what to most people would sound like a light, frothy lyric.
You don't want it to sound like hard work - you want it to sound like the sort of thing that anyone might naturally say, which just happens to be set to music. And that's the challenge of writing lyrics as far as I'm concerned.
