The music of the masses of Palestrina, woven about a well-known text, like that of the madrigals and _chansons_ of Arcadelt and Jannequin, which depended upon popular love-poems, was vague and formless. Such inner coherence as it had of itself was the result of continuous and skillful repetition of short phrases or motives in the course of the various voice-parts. In religious music these motives were for the most part fragments of the plain-song chant, nearly as old as the church itself; and masses frequently went by the name of the plain-song formula out of which they were thus built. Over and over again these bits of melody appeared, now in one part, now in another, the voices imitating each other so constantly that the style has been aptly called the imitative style. It was this style in which the great organists of the sixteenth and early seventeenth century first shaped music for the organ. It was the one principle of musical form upon which they knew how to build. Thus were constructed the _ricercars_ of the famous Andrea Gabrieli (d. 1586), Claudio Merulo (d. 1604), and Giovanni Gabrieli (d. 1612), the great pioneers. The name ricercar is itself significant. It came from _ricercare_ (_rechercher_), to seek out over and over again. Such were the pieces, a constant seeking after the fleeing fragment of a theme. Older names, originally applied to vocal music, were _fuga_ and _caccia_--flight and chase. Always there was the idea of pursuit. A little motive of a few notes was announced by one part. The other parts entered one by one upon the hunt of this leader, following, as best the composer could make them, in its very footsteps. There was a unity in this singleness of purpose, a very logical coherence, so long as the leader was not lost sight of. Little counter-themes might join in the chase and give a spice of variety within the unity. But unhappily for the musical form of these early works, the theme which began was run to earth long before the end of the piece; another took its place and was off on a new trail, again to be run down and to give way to yet a third leader. Unity and coherence were lost, the piece ambled on without definite aim or limit. There is, however, a piece by Giovanni Gabrieli in which the opening theme and a definite counter-theme are adhered to throughout. This is a rather brilliant exception, becoming as the century grows older more and more the rule until, other principles mastered and applied, composers have built up one of the great forms, the true _fugue_. Toward the end of the sixteenth century the name _fantasia_ is applied to this same incoherent form and in the seventeenth that of _capriccio_ appears. Later, at the time of Bach, the word _ricercar_ signified a fugue worked with unusual technical skill.[2]