GENERAL RULES OF PERFORMANCE
Besides tempo, accentuation, legato, staccato, phrasing, etc., which have been described in earlier chapters, other factors essential for correct interpretation were explained in many theoretical books on music published between 1750 and 1827, the year of Beethoven's death. Of all these books, Türk's Klavierschule is by far the most complete compendium of performance rules.
The theorists of the Viennese Classical Period as well as of the Style Galant and of even earlier times agreed that the performer should imitate a good singer when playing an instrumental composition. Of equal significance was the convention of "uneven playing". Arnold Dolmetsch was one of the first musicians of our own century to draw attention to the importance of this old practice and to make an exhaustive study of the subject in his book The Interpretation of Music in the 17th and 18th Centuries.
The convention of uneven playing means that accented notes were held for longer than their true value. This was done at the expense of passing notes and inevitably resulted in uneven playing. Such uneven playing was taken for granted and was therefore never marked. The same practice was applied to rests wherever they replaced accented notes.
Quantz, Versuch, 1752 (p. 113):
"[In an Allegro] where short rests appear instead of accented notes, one must take great care not to begin the note which follows the rest too soon. For example, if the first of four semiquavers is replaced by a rest, this rest must be prolonged by half its face value, as the following note must be shorter than the first one. The same applies to demisemiquavers."
The remarks of Quantz's contemporary, C. P. E. Bach, on the essence of good interpretation imply that he also took uneven playing for granted. His advice to musicians on how to play chamber music and a solo part accompanied by an orchestra give a vivid picture of the performing conventions of his time, and it also shows that these conventions were totally different from those of our own time.
C. P. E. Bach, Versuch, 1787 (p. 89, § 8):
". . . In order to avoid obscurity one must observe all rests and