The idea that singing in different styles is dangerous has been around a long time.
I guess it’s dangerous to be in a triathlon or a decathlon, too. I would venture to say that dancers who do several kinds of dance are probably at risk. Maybe instrumentalists who play classical music and jazz are also playing with fire. Actors who try Shakespeare and TV sitcoms are probably in trouble, too.
No, not because any of this is true but because people think it is. To me it’s just as bad as the people who used to say that “women’s bodies are just not made for sports” and had the “research” to prove it. Same for the people who claimed that African American’s were “not very smart” and had the “research” to prove it. And there are always people who say that the world is flat and that they can prove it. They are standing in line next to the folks who believe that humans were alive at the same time as the dinosaurs only 6,000 years ago because that’s how old the Bible says the earth is.
There is no evidence of any kind, from any credible source, that proves or even indicates that singing more than one style of music is harmful to the voice. In fact, there may even be a possibility that the people who sing more than one style hold up better and last longer than those who only sing one. It isn’t the styles that are causing problems, it isn’t the music. It is the way that the music is being sung that could create difficulties. In other words, if you don’t know what you are doing and you blunder into something that you do not understand, you can certainly hurt your vocal technique and perhaps also even your vocal folds. That is not, however, a function of diversification of vocal function. It is a symptom of vocal ignorance, and of failing to understand how to coax variable vocal behavior from your own throat through exercise over time.
Someone I have known for a very long time recently suggested to me that jumping around from one style to another is “extreme” and not good to do. He suggested that vocal problems could develop from such risky behavior. The man in question has had technical issues for 40 years and has never understood his own vocal production. He is still taking technical lessons because he can’t manage his voice without assistance. Think maybe fear is underneath that somewhere?
Fear is underneath all of these negative assessments. Fear stops most singers from really trusting the throat to do whatever you want it to do. Some few souls, however, do not have such fears and can, indeed, sing this and that with equal ease and sound appropriate, musical and expressive without any unwanted side effects.
If you are afraid to try something vocally lest it “steal” your skill away, take a look at that. If you think it will hurt you, look at how you are attempting it. If you believe that you will somehow be “changed” and not able to return to your own true self, stop and think. You cannot lose who you are unless you don’t have a good solid idea of yourself and your voice in the first place.
The only authentic danger in singing a variety of styles is falling in love with all of them and not having enough time to learn all there is to know about each one.