Two tunes from the Benjamin Cooke MS, which is available via the Village Music Project. Nothing very definite is known about Cooke or his manuscript. Chris Partington of the Village Music Project suggests a date of c1770, and describes the manuscript as follows

This neatly handwritten manuscript book forms part of the Frank Kidson Collection in the Mitchell Library, Glasgow.
The origin of the manuscript is unknown but may be northern English, due to its having been in the possession of Frank Kidson.

Neither tune seems to have been discovered (as yet) in any other source of the period, but Chris suggests “Several works between 1735-1756 by Thomas Arne involving Harlequins” as a possible source. These include a series of pantomimes performed at Covent Garden or the Theatre Royal, Drury Lane between 1735 and 1772: Harlequin Orpheus, or The Magical Pipe, Harlequin Restor’d, or The Country Revels, Harlequin Restor’d, or Taste à la Mode, Harlequin Incendiary, or Colombine Cameron, Harlequin Mountebank, or The Squire Electrified, Harlequin Sorcerer, Mercury Harlequin, and The Pigmy Revels, or Harlequin Foundling.

I learned ‘Harliquin Air’ from Matt Quinn during Geckoes soundchecks. And another member of Geckoes, Tom Miller, then introduced me to the ‘New Harlequin Air’. It’s not such a good tune, but still has a certain charm. In Cooke’s MS it’s written in D. As Chris Partington notes, this means it has some “very squeaky notes”, so Tom and I prefer to play it in G.

John Rich as Harlequin in an early British pantomime, c. 1720. From Wikimedia Commons.

Harliquin Air

New Harlequin Air

Played on G/D anglo-concertina