In any version of this song that I've heard there has always been the undercurrent of "love and lust". It is certainly a song of seduction but I would describe it as more playful than "sniggering sexuality" or "filth". Yes there are veiled references to sex but after all sex is very much a part of nature and could even be described as a miracle of sorts. Nothing in the song on a par with what one would find on MTV or even VH1. Gwilym Davies (Tradsinger) does a lovely unaccompanied version that he picked up (I think) in Dorset.   It's slow and haunting. (By the way, I enjoyed listening to the sound clips of the real nightingales).