when to use definite article

Question

This recommends "estudiando violin" but "tocar el violin."  I don't understand the rule for when to use the definite article.

Accepted Answer

Hola Erika
To simply say what your profession is we do not use the article: 
Soy violinista
Soy profesor
Soy medico
But when you add extra information, you need the article (or there is a tendency to use it):
Soy un violinista importante
Es un medico especialista en problemas cardiovasculares. 
Saludos

Answer

Hola Elizabeth
When we talk about studying a subject we drop the article:
estudiar violín
estudiar inglés
estudiar historia
When we talk about playing an instrument we use the article:
quiero tocar la guitarra, tocar el violín, tocar la trompeta
Saludos
Inma

Answer

It is written, "quiero ser un violinista importante". However, when describing profession we do not use the article: "Soy violinista." Why is the article "un" used here, in "un violinista importante"?

Thanks in advance!