Gundlach[38] found that speed was by far the most important factor in distinguishing among several pieces played to a group. And Hevner[48] found that for excitement the most important element was tempo, which must be swift. “Dreamy sentimental moods follow slow tempo. Sheer happiness demands a faster tempo.” Hanson[42] believes that “everything else being equal, the further the tempo is accelerated above _tempo moderato_ (which is about the same speed as the human pulse rate) the greater becomes the emotional tension.” He goes on to state that “as long as the subdivisions of the metric units are regular and the accents remain in conformity with the basic pattern, the effect may be exhilarating but not disturbing. Rhythmic tension is heightened by the extent to which the dynamic accent is misplaced in terms of metric accent, and the emotional effect of ‘off-balance’ accents is greatly heightened by an increase in dynamic power.” He is unduly alarmed by the effect “Boogie-Woogie” may have on the younger generation because rhythm irregularity finds its most fertile field in this jazz form characterized by “a repeated figure in the bass (which) continues indefinitely in regular rhythm.” _Sonority._ Hanson[41] has traced the development of music from the highly consonant music of the Roman Catholic Church at about the time of Palestrina to the dissonant music of certain modern composers. He describes the early hymns as “calm, serene and in a sense impersonal.” For him, “the expression of personal feeling in music seems inevitably to be associated with the use of dissonance. Indeed the expression of emotion in music seems to be bound up in the contrast between dissonance and consonance, the former producing a sense of tension and conflict to be either heightened by progression to a sonority of still greater tension or resolved by a succeeding consonance.” It may be easy for a musician to believe that the increased use of dissonance creates an increase of emotional tension, but to the musically uncultured listener dissonance may just as often create boredom or annoyance. _Composition._ Although musical factors such as pitch, intensity and melody can contribute to mood effect when isolated, the reaction to an entire composition is quite different from reaction to tones of chords. It may depend upon environment or association with the situation in which the selection was first heard or is being heard. It may be altered by the length of the composition or unanticipated contrasts of intensity or the use of unusual patterns, rhythm or tempo. In listening to music, expectation plays an important role. A sudden change or interruption is apt to excite surprise. “The mere meeting of the expectation in all its details affords pleasure of a kind. But great as is the aesthetic pleasure, a far greater degree of enjoyment may at times be attained by a carefully planned surprise, the appropriateness and artistic skill of which is recognized and approved”[10].