For a better understanding of early organ music it will be necessary here to describe briefly some of the most important and frequently-employed instrumental forms of the period. The earliest use of the organ in the church service was merely to strengthen the voice parts by duplication. When the organ was developed sufficiently to be used alone for artistic playing, the organist merely played well-known motets and other church compositions and sometimes even favorite secular madrigals and _chansons_. For a long time these were purely transcriptions of the choral parts with no attempt at variation and many of the compositions of the period were frankly written ‘either to be sung or played.’ Little by little organists ventured to introduce free passages of their own to embellish the voice parts, but such compositions remained essentially choral works. The _ricercare_ (from _ricercare_, ‘to search out’) was one of the earliest forms of strictly instrumental music, though the term was sometimes applied also to the madrigal.[97] It dates from early in the fifteenth century and was an elaborate and scholarly form into which every known contrapuntal artifice and device was introduced, and which, therefore, was least cultivated. Originally the _ricercare_ did not adhere to the same subject throughout, but, like the motet, progressed after a short elaboration to a new subject. This lacked conciseness, which, however, was won in the seventeenth century when it assumed practically the same form as the simple fugue, and for a long time these two terms were interchangeable. The _ricercare_ was sometimes in the form of a _fantasia_ on some popular melody or song and in this way many secular tunes crept into organ music as they had earlier found a surreptitious place in the old masses. A somewhat later form was the _canzona Francese_, an invention borrowed from the French _chanson_, contrapuntal in character but less elaborate than the _ricercare_ and freed from pedantry. Its first three notes were almost invariably a quarter and two eighths, thus establishing a characteristic rhythmical movement. Its song-like character made it a favorite form. The _toccata_ (from _toccare_, ‘to play’) was a third and still later form. This required brilliant execution and was in the nature of a fantastic improvisation to display the technical skill of the performer. Later it was frequently employed to precede a fugue and was built largely on the development of a single figure.