The Bantu languages have the advantage of being tonal so that allows you to pack in more information along with the rhythm. Spanish, while lacking tones, does have rhythm. This allows Mexican motorists to beep out the familiar rhythm of the obscene insult “Ch***a tu madre.” Cholos who do this have been attacked and even killed on the spot by insulted men.
Now, the rhythm of this phrase is known to gringos as the old “Shave and a haircut.” So if you’re driving in Mexico, please, PLEASE don’t give into the urge to play “Shave and a haircut”.
Cecil’s column can be found on-line at this link:
Are there really such things as “talking drums”? (18-Nov-1994)
The column (including Slug Signorino’s illustation) can be found on pages 158-160 of “Triumph of the Straight Dope”. The books can be purchased here:
Welcome to the Straight Dope Store
According to a poster in alt.usage.english who represented himself as Reinhold (Rey) Aman, Editor of Maledicta: The International Journal of Verbal Aggression, that’s almost true. You are missing a couple beats (duh), and the full phrase is “¡Chnga tu madre, cbrón!”
Aman is having trouble with the name Maledicta: "Allen spitefully, defiantly and maliciously continues to peddle devil-worshipping books and satanic-ritual shit by misusing our name “Maledicta.”
O yeh, you know what happens when the drums stop, don’t you?
When drums stop, then bass solo starts! 
> You are missing a couple beats (duh), and the full phrase is “¡Chnga tu madre, cbrón!”
The funny thing is, adding those two more beats still matches the full gringo rhythm of “Shave and a haircut, six bits.” Still dangerous!
I always thought it was “shave and a haircut, two bits.”
Yeah, apparently inflation even affects folk ditties… I liked “two bits” better anyway, as it makes for a nice pun (ok, so there’s no such thing. It’s a mean pun, then.)