Make male sound female ?

I have a song that needs both a male and a female singer. But i have no female singer. Is there any plugin or method that could make the male do both vocals ?

Just do a pitch shifter without formant preservation (these are easier to find than pitch shifters with formant preservation). Shift up a 4th or so and see how that sounds then tweak from there. It won’t be perfect but it might get by.

Ardour has pitch-shift built-in. Region > Edit > Pitch Shift. Male -> Female would be an octave usually.
Anyway, unless this is for some background choir, you’ll be better off finding some female singer or trying your best falsetto.