Most of Domenico Scarlatti's harmonic progressions are quite orthodox when considered abstractly or free of their positioning in the score. The harmonic movement is given interest by subtle alterations in time; for example, (1) simultaneous upper and lower voices of different lengths, when repeated several times, change their relationship with each other; (2) one voice may be simply delayed so that it lags behind the other voice, thus combining to produce irregular harmonic sound on many succeeding beats; (3) the combination of two or more chords appearing on one beat is similar to number (2) but does not necessarily occur more than once.