The frogs of Aristophanes

I've been hearing a chorus of frogs calling near our house for about two weeks, and I've been meaning to report that I've learned they are the Dutch version of the Greek frogs in Arisophanes' play. Not long ago we discussed frog calls here, and one unanswered question was why Aristophanes had frogs go "Brekekekex koax koax"? (Transliterated from the Greek alphabet, I assume.) Was this strange-looking call some aberration of Greek, or had frogs changed over the millennia? My best guess then was that it was the call of some species of frog that we didn't happen to be familiar with.
When the frogs calling from the pond near me started, I realized they sounded quite a bit like "Brekekekex koax koax." Maybe I'd spell it as "Weh-eh-eh-eh-eh-eh" and the second part as "Koff" or "Kow," but still it's a multi-syllabic chatter. Rather like an excited duck or sometimes like a twittering bird.
I began to listen to the sound files on the Internet again. I worked out that this had to be the "marsh frog" (Rana ridibunda). It's supposed to be found across Europe and into Asia, but not in the UK, which would account for its unfamiliarity to our UK participants. (It is a recent alien in Kent and Sussex). And what's more, there's a similar species called the "Greek marsh frog" (Rana kurtmuelleri) with much the same call.
Some sound files to listen to. They're not precisely what I hear, but close enough:
Rana ridibunda - marsh frog
http://www.club100.net/species/R ridibunda/R ridibunda Bornholm Denmark 9805 LB.mp3
R. kurtmuelleri - Greek marsh frog
kurtmuelleri/R kurtmuelleri Kerkini Gre ece 0005 LB1.mp3
For comparison, the "common frog" or "European frog" (R. temporaria) merely has a deep "Grruk."
temporaria/R temporaria Scania Sweden 9 903 LB.mp3
Once I had the name, I found that others had worked out this connection as well, such as:
http://laudatortemporisacti.blogspot.com/2004 09 01 laudatortemporisacti archive.html
One Greek animal sound that doesn't sound familiar, at least to my ear, is brekekekex koax koax, from
Aristophanes' Frogs (line 209 and elsewhere). K.J. Dover in his commentary says that "initial br-
appears in many Greek words denoting the production of sound" and also that final -x is "a Greek
spelling convention for the representation of
sounds." He concludes that "brekekekex seems thus to embody two non-representational conventions."
Apparently the Marsh Frog, Rana ridibunda, does make a sound somewhat like brekekekex with br- and -x
removed.
So that relates to Laura's original question part of the reason Brekekekex koax koax looks so strange to us is that some of the letters apparently conveyed function, not sound.
I don't remember ever reading "The Frogs"; I looked up the text and was amused to see that the frog chorus says all sorts of things, like:

http://www.mala.bc.ca/~johnstoi/aristophanes/frogs.htm
CHORUS OF FROGS:
Brekekekex koax koax
Brekekekex koax koax.
Children of the marsh and lake
harmonious song now sweetly make,
our own enchanting melodies
koax koax
The songs we sang for Nysa's lord,
for Dionysus, son of Zeus,
in Limnai at the Feast of Jars*
as people in their drunken glee
thronged into our sanctuary.
Brekekekex koax koax.
and this more frog-like passage:
CHORUS OF FROGS:
No, no. We'll sing on all the more
if we've ever hopped on shore
on sunny days through weeds and rushes
rejoicing in our lovely songs
as we dive and dive once more,
or as from Zeus' rain we flee
to sing our varied harmonies
at the bottom of the marsh,
our bubble-splashing melodies.
The frogs are not calling as much these days - I wonder if the mating season is ending.

Best Donna Richoux