A painter hangs his or her finished pictures on a wall, and everyone can see it. A composer writes a work, but no one can hear it (21) _____ it is performed. Professional singers and players have great responsibilities, for the composer is absolutely dependent on them. A student of music needs as long and as tough a training to become a performer as a medical student needs (22) ______（become） a doctor. Most training is concerned (23) _____ technique, for musicians have to be as muscularly skillful as an athlete or a ballet dancer. Singers practice breathing every day, as their vocal chords（声带） would be inadequate without (24) ______（control） muscular support. String players practice moving the fingers of the left hand up and down, while drawing the bow back and forth with the right arm, (25) ______ are two entirely different movements.
Singers and instruments have to be able to get every note perfectly in tune. Pianists (26) ______（spare） this particular anxiety, for the notes are already there, and it is the piano tuner’s responsibility to tune the instrument for (27) ______ . But they have their own difficulties; the hammers that hit the string must be dealt with carefully not to sound like drum or bass, and each tone, even if played very fast, has to sound clear.