I listen to music vs I watch television

Hola Violeta

"escuchar música" refers to listening to music in general; in this case we don't use any article. If we were more specific then the use of the article would be acceptable and sometimes necessary, for example:  "escucho la musica de los vecinos" (I listen to the neighbour's music) or "A menudo escucho la música de los años 60" (I often listen to the music from the sixties.)

With "ver la tele", this is a set expression where we always use with the article (at least in Peninsular Spanish), even though we are still talking generally. 

Saludos

Inma