How long? This could be the question I most frequently respond as a violin teacher; but honestly the truth is that for this matter it is totally relative. Each person is different: each one´s body, process and other life situations could make the difference, however, there are some common factors that influence the performance such as effort and constant practice.
Having a nice sound and good posture are directly related. The position we adopt to play the violin is particularly unique, something completely new; what you are going to do when you start playing is trying to include it in your daily life and that requires a lot of patience and discipline, specially to get adapted and to feel comfortable with it.
When you start the process of learning to play an instrument, you need to develop many motor skills, you must teach your arms and body the correct way to move in relation to the instrument; the important thing is to remember that everything is possible with effort and commitment.
The violin will start to have a more pleasant sound by the time you achieve a good position and self-control. How much time does it take you to teach your body something new? There is your answer…