The problem of the keyboard slur in the works of W. A. Mozart: A study based on contemporary treatises

The problem of how to perform the early Classical keyboard slur has prompted perplexity and dissension in generations of thoughtful performers and teachers. While the mandatory legato indicated by the slur is unquestioned, diversity of opinion centers around the performance of the last note of the slur, specifically regarding its length. Modern pedagogy has generally followed a time-honoured principle of an early release for the last note of a slur, yet many artists seem to disregard this guidance at will. This study attempts to clarify the issue by examining several treatises of the early Classical period.;A brief history of the slur is included because its origins undoubtedly influenced how it was later performed. Most of the research, however, focuses on relevant material found in three treatises written by contemporaries of Wolfgang Mozart, namely, C. P. E. Bach, Daniel Turk, and Mozart's father, Leopold. The three components of the slur---the first note, the notes under the slur, and the last note are treated in turn by presenting information found in the treatises and providing interpretative commentary. This information is then applied to slurs found in the keyboard sonatas of Wolfgang Mozart.;Unfortunately, treatises provide no definitive answer to the question of the performance of the last note of a slur. This lacuna is most likely due to the daunting task of describing the many musical circumstances involved in performing the last note under a slur. Solutions to the problem, therefore, cannot simply be founded solely on treatise instructions regarding the slur. Fortunately, the wealth of descriptive writing on the general art of effective music-making also provides some important clues to understanding the principles of performing the last note under a slur. Much of this study focuses on understanding the three important factors influencing the slur's ending: formal structure, Classical violin bowing technique and, most important, the musical context in which a slur is found. When these three aspects of performance are understood, much of the uncertainty surrounding Wolfgang Mozart's slurs will disappear.