I don't see how permission from a dead person would factor into how well you're using it, no. Just like I don't see how you'd need their permission to do a mashup of their work. I don't think it's particularly controversial for a person emulate widely known unique voices like Bowie's or Elvis's even after they're gone, and I don't see why using ML to alter your voice to do so would make that wrong somehow.
At least the stuff I've seen is usually pretty explicit about using machine learning; it's not trying to create a counterfeit (the two songs I linked are like this). I only see fans appreciating artists and sharing how songs like Fountains of Wayne's Go Hippie totally sound like an Oasis song if you put Liam on vocals.
At least the stuff I've seen is usually pretty explicit about using machine learning; it's not trying to create a counterfeit (the two songs I linked are like this). I only see fans appreciating artists and sharing how songs like Fountains of Wayne's Go Hippie totally sound like an Oasis song if you put Liam on vocals.