Since the work is so heavily ornamented, performers are obliged to arrive at decisions concerning the meaning of Mozart's musical notation for the ornaments.
Konrad Wolff offers a clear criterion, namely an appeal to the influential textbook on violin playing written (and published in Mozart's birth year 1756) by the composer's father
Leopold: "As for
embellishments, Mozart was very much his father's child, which is to say that one can find most answers by studying Leopold Mozart's
Gründliche Violinschule." Based on this criterion, Wolff judges that in general, performers should play embellishments on, rather than before, the beat – though for the main theme of the K. 511 rondo, which features a prominent triple grace note (see quotation above), Wolff allows for the possibility of playing it before the beat as well. In bars 134–135, the rising sequence of the main theme receives a particularly intense form of ornamentation: every note is trilled. : > \oneVoice a8 r8 } \new Staff { \set Staff.midiInstrument = #"fortepiano" \set Staff.midiMaximumVolume = #0.3 r8 8 8 r8 8 8 r8 8 8 r8 8 8 r8 8 8 8 } \new Voice { \voiceTwo a4. a a a a a8 } >> \oneVoice r8 r8 > } >> : (Due to software limitations, the trills and turns in the scores are not executed in the sound file.) Wolff also addresses this sort of passage, saying "trill chains must be smoothly connected, with no accent given to the new trill tone at its entrance." The basis for his advice is a piano exercise taught by Mozart to his pupil
Johann Nepomuk Hummel and recalled later by Hummel in his own textbook A number of the ornaments and variations are not notated with signs, but simply written out by Mozart in ordinary music notation. These can be taken more or less at face value, but they are of great importance for performance practice nonetheless, as they bear on issues and controversies in
historically informed performance. The reason is that many
other works of Mozart are notated quite sparely, with nothing like the layers of ornamentation he added onto the repetitions of the main theme of the Rondo in A Minor. One view is that Mozart himself, who was famed for his ability at musical improvisation, would embellish such passages on the spot. However, when serving others, as in writing cadenzas for his piano concertos (which he improvised in his own performances) or writing for publication, he would fill in the details.
Robert Levin (1990) has argued forcefully that modern performers should ornament the plainer repeated passages of Mozart scores, just as (he believes) Mozart himself did; and he faults modern conservatories sharply for failing to provide young performers with the instruction (particularly in
music theory) they would need to do this. For performers who seek to follow Levin's recommendation, works like the Rondo in A Minor are of great value: the finished work, written out so painstakingly, is a sort of compendium of Mozartean ornamentational technique from which the modern player can learn. To help make this point, Levin juxtaposes all ten appearances of the Rondo's main motif in musical notation, illustrating the striking variety of decoration and restatement that Mozart achieved. One of the ways in which the main theme is decorated appears at measures 86–87: it is much like the ornamentation of measures 5–6, but the melody notes that would normally appear on the musical beat are delayed slightly, with a sixteenth rest appearing on the beat instead. The left hand plays on the beat as usual.
Measures 5–6: : > \oneVoice a8 r8 } \new Staff { \set Staff.midiInstrument = #"fortepiano" \set Staff.midiMaximumVolume = #0.3 r8 8 8 r8 8 8 r8 8 8 r8 8 8 r8 8 8 8 } \new Voice { \voiceTwo a4. a a a a a8 } >> \oneVoice r8 r8 > } >>
Measures 86–87: : > \oneVoice a8 r8 } \new Staff { \set Staff.midiInstrument = #"fortepiano" \set Staff.midiMaximumVolume = #0.3 r8 8 8 r8 8 8 r8 8 8 r8 8 8 r8 8 8 8 } \new Voice { \voiceTwo a4. a a a a a8 } >> \oneVoice r8 r8 > } >> This kind of ornamentation has been identified as the 18th-century version of
tempo rubato; the left hand accompaniment remains steady, but the right hand imposes a slight delay in the melody notes. Further discussion of this practice, with reference to K. 511 but also citation of 18th-century authorities, was provided by Roland Jackson. The practice was described by Mozart himself in a letter to his father. ==Critical reception==