Music teachers will probably say that professional music starts with a theory. Only after learning notes and other aspects of music theory, it is possible to sing well. However, there are some good singers who don’t know anything about music theory. They don’t even know the notes, but their voices sounds well anyway, because they can learn by listening. So is it really a necessity to learn music theory to become a singer, or is it just imposed rule.
The biggest issue is that if you want to become a better singer, you will need to do the music trainings and mostly they are based on music theory. For example, one of the most common ways to train the voice register and height is to hit a note on the piano and try to sing it. If you don’t know the notes, you cannot do this practice. Also other trainings are based on similar principles, so to do them singer need to learn the notes and music language. Those singers how can tell the difference between sounds just by listening can try to manage without knowing notes, but it still restricts the learning process. That means training your voice will be lot harder without knowledge about music theory.
If you really want to start professional singing career without knowing notes and anything of music theory, also be ready that you will need a help form assistants. It will dramatically complicate the practical part of your work. You won’t be able to sing any song, you haven’t heard before, because notes mean nothing to you. So you will need someone who translates this music language. It will definitely encumber your work.
So you see that not knowing music theory really complicate the task of becoming a singer, but actually there are also some benefits from not knowing notes and learning by hearing. Lot of singers admits that knowing music theory interfere to their ability of improvises. If song is not written on the page with notes, they don’t know how to sing it. Any singer needs to be able to improvise and sing in their own, unique manner, otherwise their singing gets boring. Then maybe it is even good to knot know the notes?
Actually, it all depends on the singer itself. If you don’t know the notes and it doesn’t disturb you to become a better singer, you don’t need them. If your voice is really good, it is improving and also you don’t have any practical problems with singing the songs, because of not knowing the notes, then you really don’t need them. Even if the representatives of academic music will deny that, it is possible to sing without knowing the music theory.
However, if you feel that lack of this knowledge disturbs you in any way, start learning it. Most of the people are not so gifted to sing perfectly only by listening, so if you have serious attentions on singing, than take some time to learn music theory.