Such a scheme falls naturally into four divisions, plainly differentiated from each other in respect of the style of composition and the manner of performance, both determined by the nature of the instrument employed and the status of the musical idea.  Simply for the sake of convenience let the period represented by the first group be called the classic; the second the classic-romantic; the third the romantic, and the last the bravura.  I beg the reader, however, not to extend these designations beyond the boundaries of the present study; they have been chosen arbitrarily, and confusion might result if the attempt were made to apply them to any particular concert scheme.  I have chosen the composers because of their broadly representative capacity.  And they must stand for a numerous epigonoi whose names make up our concert lists:  say, Couperin, Rameau, and Haydn in the first group; Schubert in the second; Mendelssohn and Rubinstein in the third.  It would not be respectful to the memory of Liszt were I to give him the associates with whom in my opinion he stands; that matter may be held in abeyance.

[Sidenote:  Predecessors of the pianoforte.]

[Sidenote:  The Clavichord.]

[Sidenote:  "Bebung."]

The instruments for which the first group of writers down to Haydn and Mozart wrote, were the immediate precursors of the pianoforte—­the clavichord, spinet, or virginal, and harpsichord.  The last was the concert instrument, and stood in the same relationship to the others that the grand pianoforte of to-day stands to the upright and square.  The clavichord was generally the medium for the composer’s private communings with his muse, because of its superiority over its fellows in expressive power; but it gave forth only a tiny tinkle and was incapable of stirring effects beyond those which sprang from pure emotionality.  The tone was produced by a blow against the string, delivered by a bit of brass set in the farther end of the key.  The action was that of a direct lever, and the bit of brass, which was called the tangent, also acted as a bridge and measured off the segment of string whose vibration produced the desired tone.  It was therefore necessary to keep the key pressed down so long as it was desired that the tone should sound, a fact which must be kept in mind if one would understand the shortcomings as well as the advantages of the instrument compared with the spinet or harpsichord.  It also furnishes one explanation of the greater lyricism of Bach’s music compared with that of his contemporaries.  By gently rocking the hand while the key was down, a tremulous motion could be communicated to the string, which not only prolonged the tone appreciably but gave it an expressive effect somewhat analogous to the vibrato of a violinist.  The Germans called this effect Bebung, the French Balancement, and it was indicated by a row of dots under a short slur written over the note.  It is to the special fondness which Bach felt for the clavichord that we owe, to a great extent, the cantabile style of his music, its many-voicedness and its high emotionality.