We have said that one must not invariably interpret, by their present meaning, certain expressions whose significance is no longer the same as when Bach wrote. First of all, the term _Organo pleno_, sometimes the sole indication given by Bach for preludes, fugues, or fantasies; one is often tempted to interpret it, on modern organs, by calling into requisition the uproar of all the registers combined, to whatever family they may belong. Let us see what was understood in Bach's time by _organo pleno_, or _volles Werk_. "The _volles Werk_," says Mattheson,[150] "consists of principals, Sordunen (the bourdons of to-day), salicionals, octaves, quints, mixtures, _Scharffen_ (small-scale mixtures of three ranks), of the quintadena, cymbale, nazard,[151] twelfth, sesquialtera,[152] and of super-octaves; with the _Posaunen_ in the pedal, but not upon the manual; for the _Posaunen_ are reeds, which are not drawn upon the manual with full organ, where, on account of the higher pitch, they would be too rasping; in the pedal, on the contrary, through the sonority of their tones, they produce a majestic effect, especially if the mouths of the pipes are covered, as is desirable." [Footnote 150: _Der Vollkommene Kapellmeister_, Hamburg, 1739, §69, p. 467.] [Footnote 151: Mattheson says, _à propos_ of this stop: "The French have given to the _Nachsatz_ (thus named on account of its high pitch, in contrast to the _Untersatz_ of thirty-two feet) of the Netherlanders, the designation _Nasard_ or _Nasarde_, 'a vulgar expression, of which use is made in comedy or burlesque,' says Boyer's dictionary."] [Footnote 152: This register, composed of two ranks of pipes of tin or of composition, is a compound stop. The longer pipe gives the fifth of the octave, the shorter the third of the fifteenth; there is thus the interval of a major sixth between the two ranks.] In a former work, Mattheson had laid down the following rule for omitting the reeds from the _ensemble_ of the registers:[153] "A reed-stop may not be drawn with the flutes upon the same keyboard, unless it be in the pedal." He makes an exception only in case the organ is not sufficiently powerful to keep a choir from wandering from the pitch and into chaos, when advantage must be taken of all resources. [Footnote 153: In _Das neu eröffnete Orchester_ (1717). Mattheson was born in Hamburg in 1681; aside from his critical works on music he was an organist of ability; he knew Buxtehude, becoming acquainted with him in 1703. He even expected to succeed him, but renounced his aspirations in this direction upon learning that in accepting the position of the father he would be obliged to marry the daughter, Anna Margaretha, born in 1669, and therefore much too old for him; this was one of the conditions of the place, which also deterred Händel from presenting himself as a candidate.]