This is simply a borrowing in of the musical direction indicating that a composition be played in a ‘spirited or boisterous manner’ or in an ‘impetuous, boisterous style’ and hence gives is a clue to the character of the individual.
The Hell here at Cr—ckf—rd’s
This denoted Crockfords, the popular name for William Crockford's ‘St James's Club’, founded in 1823 in premises in St James Street, London. the St James was a Gentlemen’s Club which became one of Europe’s most famous gaming houses.
A ‘hell’ in this context is merely a gambling house. Per the OED:
A gaming house; a gambling den
At the website Victorianweb.org we read in the history of the Crockford Club that:
The rules and regulations were made more stringent, because several notorious black-legs had obtained admission;
The relevant definition for Black-leg may be:
depreciative. A swindler, esp. a swindling bookmaker.
Though as this is particularly associated with racetracks, I have some reservations and think there may have been a related but distinct use more appropriate to gaming houses than horse races.
There is also the definition
A person who fails or refuses to join his or her colleagues for a particular purpose, or who breaks the rules of a trade or group.
So it may possibly just mean ‘rule breaker’, though the OED gives this example of a compound construction which may give a hint:
1767 St. James's Chron. 24–6 Dec. Members of the Black-leg Club..unanimously agreed..that the said Ketch be expelled.
I thought at first that this suggested that there may have been an actual ‘Black Leg Club’ whose members infiltrated the Crockford, but found a fuller rendering of the quote in The New Foundling Hospital for Wit, under the heading ‘Humorous Advertisements’.
Whereas a person, who stiles himself Esquire Ketch, has falsely and scandalously aspersed the characters of several gentlemen, members of the Black-leg Club; it is unanimously agreed, at a meeting of the Black-leg Club held this day at the Pillory and Tumbrel Tavern, Tyburn, that the said Ketch be expelled the old hazard-room called Hell, at Newmarket; a society instituted purposely to exclude all persons, except those whose conduct and characters entitle them to be received into the company of gentlemen.
To this is appended a list of names including such luminaries as Mat o’the Mint, Tricking Tom, Anthony Sweepstakes, Will. O’the Turf, and Anthony Win-all.
The whole appears to be a parody, possibly invoking the previous century’s executioner ‘Jack Ketch’, of an advertisement posted the same day in the London Evening Post in December 1767 whereby the Jockey Club expelled somebody from their new coffee room at New-Market for conduct unbecoming, so the Black-Leg Club was not a real thing and this whole section has been a blind alley.
I post it merely to save anyone else the trouble of exploring it and to underline the association of Black-legs with horse-racing, but also via the Ketch connection, with Satan.
Because of his botched executions, the name "Jack Ketch" is used as a proverbial name for death, Satan and executioners.
Wikipedia: Jack Ketch
All of which seems to come down to
a black-leg despatch
Meaning something like, ‘a messenger drawn from the ranks of the swindlers who have infiltrated the Crockford’.
The Panic of 1826 was, per Wikipedia
a financial crisis built upon fraudulent financial practices from the management of various firms. The height of the panic occurred during July 1826 when six of the sixty-seven companies publicly traded on the New York Stock Exchange abruptly failed. Within the coming months, twelve more NYSE firms would also fail. The panic sparked New York State to bring in extensive legislation seeking to regulate financial companies and protect investor interests. These regulations, legislations, and precedents like the shareholder derivative precedent were some of the first ever enacted in America and provided the basis for today's financial regulations after the panic of 2008.
Therefore the mischief Don Strepitoso has done in the Panic, is probably enabling or committing the ‘fraudulent practices’.
There was a General Election in 1826, which (which again resorting to Wikipedia)
saw the Tories under the Earl of Liverpool win a substantial and increased majority over the Whigs. In Ireland, liberal Protestant candidates favouring Catholic emancipation, backed by the Catholic Association, achieved significant gains.
There had been significant developments in Irish politics since the 1820 general election. Whilst Catholics in Ireland—who met the normal property qualifications—had been permitted to vote since before the Union, they were still not eligible to sit in the United Kingdom Parliament. The right for Catholics to serve in Parliament was known as a measure of Catholic emancipation. In 1823, Daniel O'Connell started a campaign for repeal of the Act of Union, and took Catholic Emancipation as his rallying call, establishing the Catholic Association.
From 1826, the Catholic Association began to support pro-emancipation candidates in elections. The Association used its money and manpower to campaign for candidates to be elected into Parliament, to pressure the government from within to pass Catholic emancipation.
The ’Penal Code’ mention is almost certainly in reference to Robert Peel’s reforms when he was Home Secretary. He greatly reduced the number of Capital Crimes and brought in some reforms to prisons, ending the practice of holding prisoners in chains, instituting wages for gaolers so that they didn’t have to make money from their prisoners, etc.
The Black Act was repealed in 1823. The Black Act had introduced the death penalty for over 350 criminal acts.
Robert Peel was Minister for Ireland between 1812 and 1818, there may be a link there to the anti-catholic theme, but I’m not familiar enough with the Irish politics of that (of any other) period to make a sally into that.
Eld-n has been identified by @Kimchilover as John Scott First Earl of Eldon, and this seems correct.
Although labelled a Tory by the opposition and by subsequent historians, Eldon placed himself long-term in the Whig tradition, defending "a doctrine essentially similar to that which ministerial Whigs had held since the days of Burnet, Wake, Gibson and Potter". As an Ultra-Tory, protesting against Catholic Emancipation, he sat with the Whigs during the 1830 parliamentary session and in 1825, following the defeat of the Tory Sir Francis Burdett's Emancipation Bill in the House of Lords by a majority of 48, drank "the 48, the year 1688, and the glorious and immortal memory of William III".
This would fit very well with the attempt to ‘get up a thundering No-Popery cry’.
I assume the Devil generally enjoys conflict and conniving at oppression of Catholics in Ireland via politics would be just one avenue to foment it.
The Sans-Culotte crew is clearly reference to the French revolutionaries
The sans-culottes, literally "without breeches" were the common people of the lower classes in late 18th-century France, a great many of whom became radical and militant partisans of the French Revolution in response to their poor quality of life under the Ancien Régime.
The claim that they could make their cry more popular than the Marsailles because they not only have men who wear breeches, but ones who wear petticoats, may be a reference to Molly-Houses
a term used in 18th- and 19th-century Britain for a meeting place for homosexual men. The meeting places were generally taverns, public houses, coffeehouses or even private rooms where men could either socialise or meet possible sexual partners.
Cross-dressing is known to be one of the activities that could perhaps only be carried out in such places, it is possible that the Crockford Club allowed for cross-dressing, or it is also possible that the reference is back to the earlier line
That yell which when chorused by laics and clerics
And is actually a reference to having clerics in their ‘band’, refering to their vestments as petticoats.
The ‘Treasury’ may be referring to The 2nd Earl of Liverpool, being the Prime Minister and First Lord of the Treasury at that time.
By the 1820s he was the leader of a reform faction of "Liberal Tories" who lowered the tariff, abolished the death penalty for many offences, and reformed the criminal law.
Wikipedia: Robert Jenkinson, 2nd Earl of Liverpool
‘The Treasury pitch-pipe of late is so various’ would then be a reference to the reform of the penal code discussed earlier and a softening of attitudes to Irish Catholics.
‘And certain base voices, that lookt for a fee At the York music-meeting now think it precarious.’
The York reference is difficult, but I’m wondering if it is related to the Luddites and if ‘music-meeting’ is somehow a reference to the mass trial of Luddites in York in 1813. Perhaps politicians who were vocal in condemnation of the Luddites are now more fearful of the Public's opinions. Some of the sentences handed down at that trial may not have been possible by 1826 due to the reforms to the penal code.
As it happens, the original Luddite, Ned Ludd, is often depicted in a dress as this was apparently the common habit for disguise when committing illegal acts. So another possibility for the petticoats.
‘Doctor Wise’ I have difficulty pining down, there have been a lot of people of that name. One potential, who I can find no record of having a doctorate, but is otherwise in the right place at the right time, is Thomas Wyse:
Wyse was educated at Stonyhurst College and at Trinity College Dublin, where he distinguished himself as a scholar. After 1815 he passed some years in travel, visiting Italy, Greece, Egypt and Palestine. In 1821 he married Princess Letizia Bonaparte (1804–1871), daughter of Lucien Bonaparte, and after residing for a time at Viterbo he returned to Ireland in 1825, having by this time inherited the family estates.
He now devoted his great oratorical and other talents to forwarding the cause of Catholic emancipation, and his influence was specially marked in his own county of Waterford, while his standing among his associates was shown by his being chosen to write the address to the people of England.
In 1830, after the passing of the Catholic Relief Act 1829, he was returned to parliament for the Tipperary constituency, and he attached himself to the Whig Party and voted for the great measures of the reform era.
This would tie in with the earlier references to the importance of Catholic Emancipation in the 1826 General Election, but as he is a proponent rather than opposer of it, I'm not completely sure he's the right dude.
Huntingdon Maberley is likely to refer to Frederick Herbert Maberley:
In 1826 he took an active part in the opposition to Lord John Russell's re-election for the county of Huntingdon.
Wikisource: Maberley, Frederick Herbert
So what is Moore’s ‘point’? This is where I am least sure of my ground, but I take it that, from his base in a diabolic gentleman’s club the Don is reporting to his boss that he has been doing his best to promote misery, and that to make up for the loss of the old, harsher penal code, he had hopes to get up some rousing anti-popery sentiment in the elections, but public opinion actually swung in favour of Catholic Emancipation and that with all this change going on he could scarcely get a decent anti-catholic chorus going.
So, the point being that the treatment of Ireland has been diabolic, but now despite some people's best efforts, the good Christians were actually getting a bit more Christian to each other? Except I'm not sure that's terribly satirical.