I’ve heard this from a number of places.
Certainly there is a time in your practice room to just try stuff…
But mostly you don’t sing what you don’t hear in your mind first.
In other words…you don’t wing it…
You fully hear it..and then try to replicate what is in your inner ear.
Now copying MP3 recordings of your favorite singers will get you in the habit and practice of copying what you hear.
So when Sam Cooke sings a run…you hear it first…
Then you copy it…
That way, later when you hear something in your mind…
You got practice copying notes…
In addition, copying other singers will place things in your inner ear that you will later come together in interesting and different ways…
So again…you must copy the recordings of great singers and it will help you in many ways.
And it will place things in your ear that you can copy…
English