Consonance, says the dictionary, is the combination of several tones into a harmonic unit. Dissonance results from the deranging of this harmony by the addition of tones foreign to it. One must admit that all this is not clear. Ever since it appeared in our vocabulary, the word 'dissonance' has carried with it a certain odor of sinfulness. Let us light our lantern: in textbook language, dissonance is an element of transition, a complex or interval of tones that is not complete in itself and that must be resolved to the ear's satisfaction into a perfect consonance.