Clarity in musical communication depends on the skillful and sensitive development of a limited number of strong musical ideas. An excess of undeveloped ideas results in vague or incoherent musical statements, while aimless repetition of even the most interesting idea soon becomes monotonous or even ridiculous. The success of both composition and improvisation depends on a proper balance between unity and variety. Unity is properly achieved by limiting the number of ideas to be included in a composition or improvisation. Variety is properly achieved by developing these ideas in an interesting and meaningful way. ??
Bill Dobbins, The Contemporary Jazz Pianist, Vol. 2 (East Providence: GAMT Music Press, 1978), 3.