This quote is from Act I, scene iii of Henry VIII. Here's your quote, in the context of the scene:
. . .Now I would pray our monsieurs
To think an English courtier may be wise,
And never see the Louvre.
They must either,
For so run the conditions, leave those remnants
Of fool and feather that they got in France. . .
And understand again like honest men. . ..
What a loss our ladies
Will have of these trim vanities!
There will be woe indeed, lords; the sly whoresons
Have got a speeding trick to lay down ladies.
A French song and a fiddle has no fellow.
The devil fiddle 'em! I am glad they are going,
For, sure, there's no converting of 'em.
This exchange is in reference to a "proclamation" that English courtiers reform their French-i-fied ways and begin to behave like honest Englishmen, unsullied by the debauched ways of the French. The "French song and a fiddle" is reference to the smooth moves that the right music and atmosphere can produce for seducing a lady. This is why Lovell, above, refers to use of these two things as a "speeding" or successful "trick."
The English and French, during Shakespeare's day, enjoyed a rivalry of culture. Shakespeare is making fun of how focused on silly entertainments and seducing women the English young men who travel to France become.
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