In the new print of the Yabia Omer 1:siman 6 footnote 9 he writes that Rav Eliyashiv mattired (allowed) one from hearing kol isha from the radio even if the person recognizes the singer,since the voice isn't real rather it is sound waves from the electricity. This opinion is quoted in שו"ת ישיב משה טורצקי  pg.14. The footnote also notes the מהרש"ג חלק ג סימן זה אות ב. I believe the Bnei Banim addresses this issue as well.

It must be noted that all would agree that if one would have sinful thoughts because of listening to the music then it would be prohibited entirely.