Very simple: Making Music. Sounding musical in everything you do is the single most important aspect of playing the instrument. I learned this the hard way. My teacher, God bless him a great guy - never really made me sound musical when I practiced. It was all about technique; building my range with Claude Gordon exercises, Flexibility with Irons, tonguing and fingering with Herbert Clarke exercises 2 hours a day. Breathing exercies - just about everything. I became a master at playing trumpet exercises, but when I went to college I struggled at making a simple tune sound pretty on the horn. That's my advise: Whatever you do, play musically - and practice songs - LOTS of them - everyday!