[Avodah] Fw: R' Unna: psak or hetter?

[SBA]

From: "Chaim G Steinmetz"
 R' Unna's teshuvah on girls'choral groups is now available on
>> http://www.aishdas.org/avodah/faxes/shoalin.pdf
> In that tshuva he forbids kol isha of an ervah, .. - says there is no 
chiyuv macho'oh concerning) girls that are not ervah.
> I fail to see how this tshuvah helps concerning opera etc. 
 In addition, according to many nida is also considered ervah 
which would cause a problem even concerning single
> Jewish girls.  (SBA old: The MB 75:17 says this - beshem Achronim.)

And even R. Unna, whilst for some reason, overlooking the nidah problem,
(at least legabei chiyuv of machoeh), writes "lo yimche bifresiyeh
 ki yesh lochush bizman hazeh sheyilaagu alav.." 

Thus his reasoning for this psak is  because 'yilaagu alav' - obviously 
realising that the community of the questioner would have 
disregarded any such machoeh.

Had his psak - which some here have used as a basis for a
 'hetter'  for kol isha - been universal and lekatchilah, there would 
be no reason for him to add those words.

And even so, he is talking about a machoeh 'bifresyieh', implying that 
privately a machoeh may indeed be in place.

SBA