hi

I agree with all of the above. You need both.

In my case as a guitarist and vocalist I use the dots to learn the tune , or the approximate tune, as I know I will almost certainly not play exactly as the written music "demands".

On the guitar particularly for folk music I can usually work out what and how I want to play. For some pieces and when I am feeling particularly lazy I will not use the dots but from the chord diagrams where they are provided. Or sometimes I use the tablature if it is available.

I do not believe that one plays by ear - rather I think you play from memory. But most will argue that it is the same thing.

cheers

MikeL2