Conspiracy Theories: "Little Sir Hugh" is a seven hundred year old mediaeval ditty about the Blood Libel, the assertion that Jews stole away good Christian children for nefarious purposes. The band edited out the anti-Semitic aspects of the song.
Epic Rocking: "King Henry" from Below the Salt comes in at about 7 minutes. And it rocks out without drums.
"Allison Gross" is another example. If you never believed drumless, guitar-driven folk-rock could sound loud, harsh, and abrasive, you will now.
Getting Crap Past the Radar: "Drink Down The Moon", the sort of English folk song Puritans would not have appreciated at all, and which needed to have its principal theme slightly disguised. The same applies to slice of thinly disguised paganism like "Seven Hundred Elves", and the occasional hint of Celtic dissidence, which the English state and church would not have appreciated. And you thought folk music was twee and safe?
Intercourse with You: Drink Down The Moon, eight minutes of robust rural English sex circa 1400, disguised as ornithology. "The Two Magicians", in which a wizard and a witch get it on. "Spotted Cow" and "Bonny Black Hare", where finding animals leads to finding fun times (the latter with a gun/penis metaphor). "King Henry", in which good old loving turns a monstrous hag into a beautiful woman. "Royal Forester", who uses his (alleged) title to sleep with a woman he finds. "The Ups and Downs" and "The Gentleman Soldier", both dealing with a woman sleeping with a soldier who then leaves her. And that's just songs where the main characters are actively getting it on.
Indeed, the song "Spotted Cow"'s other appearance in English literature is in the early chapters of Thomas Hardy's Tess of the D'Urbervilles, where it presages the later events of the novel.
Mood Whiplash: "Jack Hall" is a cheerful, rousing, upbeat song about...a murderer headed for the gallows. Likewise "Sir James the Rose", about a murderer on the run who gets a bloody comeuppance. Then there's "Dance with Me", a jolly jig about an elf princess who gaily tries to persuade a knight to dance with her - and then, when he refuses, strikes him an almighty (and possibly lethal) blow.
Peter Sellers: Guests on "New York Girls", playing the banjo and supplying vocal interjections as Henry Crun, Minnie Banister and Major Bloodnok of The Goon Show.
Revolving Door Band: Maddy Prior compared Steeleye to a bus, with members (even including herself at one point) getting on and off. Indeed, the band were aware of this; on Now We Are Six, there is a jokey rendition of "The Camptown Races" in the voice of a West Indian bus conductor that alludes to this.
The Span's version of the old English ballad The Two Magicians directly inspired the account of the magical duel between witch and wizard in Equal Rites. And "The Ups and Downs" inspired "The Ins and Outs" in Monstrous Regiment. There is a Steeleye Street in The Compleat Ankh-Morpork in acknowledgement of the connection.