sequence

repetition of a melodic idea at a higher or lower pitch

More or less exact repetition of a melody (with or without its harmony) in the same part at another level. If the repetition is only in the melody (the harmony being changed) it is a melodic sequence, if in the harmony also, a harmonic sequence. Italian Baroque Music often used harmonic and melodic sequences based around the circle-of-fifths. Sequence is a fundamental device used in late-Baroque (especially Corelli's) music. The sequence, whether carried out diatonically within one key or modulating downward in the circle-of-fifths, is one of the most powerful agents in establishing the tonality.