Many of the lines in the "Major-General's Song" from Pirates of Penzance are incomprehensible to the average person today, such as references to "the crimes of Heliogabalus" or "The Frogs of Aristophanes." My questions is: was the song understood by Gilbert and Sullivan's contemporaries?
Here are the lyrics in question:
I am the very model of a modern Major-General,
I've information vegetable, animal, and mineral,
I know the kings of England, and I quote the fights historical,
From Marathon to Waterloo, in order categorical;
I'm very well acquainted too with matters mathematical,
I understand equations, both the simple and quadratical,
About binomial theorem I'm teeming with a lot o' news---
With many cheerful facts about the square of the hypotenuse.
I'm very good at integral and differential calculus,
I know the scientific names of beings animalculous;
In short, in matters vegetable, animal, and mineral,
I am the very model of a modern Major-General.
I know our mythic history, King Arthur's and Sir Caradoc's,
I answer hard acrostics, I've a pretty taste for paradox,
I quote in elegiacs all the crimes of Heliogabalus,
In conics I can floor peculiarities parablous.
I can tell undoubted Raphaels from Gerard Dows and Zoffanies,
I know the croaking chorus from the Frogs of Aristophanes,
Then I can hum a fugue of which I've heard the music's din afore,
And whistle all the airs from that infernal nonsense Pinafore.
Then I can write a washing bill in Balylonic cuneiform,
And tell you every detail of Caractacus's uniform;
In short, in matters vegetable, animal, and mineral,
I am the very model of a modern Major-General.
In fact, when I know what is meant by "mamelon" and "ravelin",
When I can tell at sight a chassepôt rifle from a javelin,
When such affairs as sorties and surprises I'm more wary at,
And when I know precisely what is meant by "commissariat",
When I have learnt what progress has been made in modern gunnery,
When I know more of tactics than a novice in a nunnery:
In short, when I've a smattering of elemental strategy,
You'll say a better Major-General has never sat a gee---
For my military knowledge, though I'm plucky and adventury,
Has only been brought down to the beginning of the century;
But still in matters vegetable, animal, and mineral,
I am the very model of a modern Major-General.
The purpose of the song is to show that the singer is erudite, and very well educated. Using terms, some of which would go over the heads of much of the audience is part of the point of the song.
However, many of the classical references would be understood by those who'd paid attention during their 'classical education'.
Aristophane's play 'The Frogs' would have been read in Greek; the late and (very) dissipated teenage Roman emperor Heliogabalus would have been covered in history, and was also enjoying a revival of popularity among the Decadents at the time.
Other terms, such as "mamelon" and "ravelin" were specialized military jargon (for parts of fortifications).
I suspect that the intended contemporary audience would have had a reasonable notion of much of what was being discussed, but almost no one would have gotten every reference.
Which is exactly what G&S intended.
Readers may find this helpful: http://gsopera.com/lexicon/operas
I can't say for sure whether they would have gotten every reference, though some are less obscure than others, obviously. I went and perused some reviews in New York from the time when it premiered, and I'm seeing that the reviewers recognize that it's supposed to be a caricature. One review on January 1, 1880 describes Major-General Stanley as "quite an absurd personage" and that the operetta makes a "number of good points." It's hard to know exactly what that means, but my reading of it is that this reviewer saw the satire and, while they may not know thoroughly all the references, recognizes what is a reference when it passes by. Naturally, this is an American reviewer, so there are probably references that they didn't get that British audience members would have, but suffice it to say that it seems that if the references weren't known, their function was understood.
I will say, though (and I think it's important to the significance of the song), that the song is intended to be a parody of the "educated and well-rounded" military officer, which fits in to the character of the whole operetta, which parodies a number of things, from culture and character to the music itself, which references stylistic tendencies of the time and the preceding generation of composers. Gilbert and Sullivan were really smart, and Sullivan was a really skilled composer!