I've been thinking about this for awhile and I have been wondering which is considered to be more difficult, or is there no difference. On the Piano I play both hands and multiple lines of harmony, along with the melody. On the trumpet I am only playing one line of music whether it be melody or harmony. Is one considered to be more difficult musically, or is each difficult in it's own right. I am aware that string instruments like the violin do occasionally play 2 lines together, and organs and other keyboard and similar instruments play multiple lines at the same time.