I often ponder if a teacher / tutor doesn't approach their own interpretation of written music just as a conductor does. As example, traditional written tempo has quite a bit of latitude, thus what precise metronome setting is correct? Or, must we play the music in the key in which it is written, which as trumpeters we seldom do? As to this latter, I believe we must be adept at key changes as there is a lot of music that calls for such, an example being "Amazing Grace". No, I don't think the Arban's explicitly stated "HOW", but it certainly provided the development of skills with his music studies (etudes) / exercises.