Need help with robotic vocals.

I am having trouble turning the vocals of a song my friend recorded into a robotic effect I have used vocoder as well as the echo effect and I did get the vocals to sound like a robot but the problem is it also effects the sounds/instruments of the song as well is there any way to isolate the vocals make them robotic then put them (vocals and sound) together again.

Thanks

Yes. That’s correct. You can’t take apart a mixed song into individual instruments and voices. If you have the original instruments and voices on their own tracks, then you can treat any instrument or voice as you like and then combine them all into a new song or performance.

Koz