Another important feature of the musical education is the hearing of good music artistically performed. Vocal students should be urged to attend the opera and the orchestral concerts. They should become familiar with the different forms of composition by actually hearing the masterpieces of music. Chamber music concerts, song recitals, and oratoric performances,--all are of great advantage to the earnest student. When students attend the opera, or hear the great singers in concerts and recitals, they should listen to the singers' tones, and not wonder how the tones are produced. _Ear Training_ No special exercises can be given for the training of the ear. The sense of hearing is developed only by attentive listening. Every vocal student should be urged, and frequently reminded, to form the habit of listening attentively to the tones of all voices and instruments. A highly trained sense of hearing is one of the musician's most valuable gifts. A naturally keen musical ear is of course presupposed in the case of any one desiring to study music. This natural gift must be developed by exercise in the ear's proper function,--listening to sounds. Experience in listening to voices is made doubly effective in the training of the ear when the student's attention is called to the salient characteristics of the tones heard. In this regard the two points most important for the student to notice are the intonation and the tone quality. Absolute correctness of intonation, whether in the voice or in an instrument, can be appreciated only by the possessor of a highly cultivated sense of hearing. Many tones are accepted as being in tune which are heard by a very keen ear to be slightly off the pitch, or untrue to the pitch. This matter of a tone being untrue to the pitch is of great importance to the student of music. Many instruments, when unskilfully played, give out tones of this character. The tones are impure; instead of containing only one pitch, each note shades off into pitches a trifle higher, or lower, or both. This faulty type of tone is illustrated by a piano slightly out of tune. On a single note of this piano one string may have remained in perfect tune, the second may have flatted by the merest fraction of a semitone, and the third by a slightly greater interval. When this note is played it is in one sense not out of tune. Yet its pitch is untrue, and it shades off into a slightly flat note. In the case of many instruments, notably the flute, the clarinet, and the French horn, unskilled performers often play notes of this character. But in these instruments the composite character of the note is vastly more complex than in the piano. A very keen ear is required to appreciate fully the nature of this untrueness to the pitch. But this is exactly the kind of ear the singer must possess, and it can be acquired only by the experience of attentive listening.