Dissonance has been defined differently by different people in different places at different times. Western musical history can be seen as progessing towards a wider definition of consonance, culminating in the "emancipation of the dissonance", such as in the view of Arnold Schoenberg. Henry Cowell viewed tone clusters as the use of higher and higher overtones. While the perception and definition of dissonance is obviously culturally influenced, dissonance may also have some objective basis. In general the closer the frequencies of two pitches the more dissonant they are. As two pitches approach each other they begin to produce beat oscillations, which are caused when the two pitches cause interference, or reinforce and cancel each others amplitudes. Consonance between two notes may also be defined as greater coincidence of their harmonics or partials, which collectively are overtones. Dissonance is then defined by the amount of beating between non-common harmonics. By this definition dissonance is dependent not only on the quality of the interval between two notes, but the harmonics and thus sound quality (timbre) of those notes themselves.

In music, dissonance is the quality of sounds which seem "unstable", and have an aural "need" to resolve to a "stable" consonance. Both are words applied to harmony, chords, and intervals. The most strict definition of dissonance includes all sounds which are considered "unpleasant", while the most general definition includes only those which are restricted in their use.

From the beginning of music history, people have been struggling with their conceptions of consonance and dissonance. There even seems to be much disagreement to the meanings of the words themselves. Consonant sounds have been defined as agreeing, pleasant, satisfying, and restful, and have been explained by simple ratios and the harmonic series. Dissonant sounds, on the other hand, have been seen as harsh, inharmonious, unresolved, and unpleasant, but are often believed to be the most interesting and beautiful sounds in music. From as far back as Pythagoras and Aristoxenus, philosophers, theorists, composers, and critics have been battling over how to deal with consonance and dissonance.
It seems that several factors determine our conceptions of consonance and dissonance. Mathematics (simple ratios), the harmonic series, sympathetic vibration, the relationship to a tonal center, musical knowledge and exposure, as well as cultural and psychological factors affect what we see as consonant and dissonant. These four Studies in Consonance and Dissonance, for solo piano, experiment with some of these factors through the manipulation of intervallic relationships, especially in relation to a tonal center, the harmonic series, and simple ratios; the statement of material both modally and bi-modally; the creation of synthetic scales of varying degrees of C & D through the combinations of different tetrachords; and the exploitation of different styles.