The performer must always ask themselves why they are applying rubato at any given point in the music. And, it is advisable to consider how the use of rubato when playing will affect the listener’s understanding and enjoyment of the piece.
Rubato is an Italian word meaning robbed time. There are two types of rubato, one where the accompaniment is kept in strict metronomic time and the melody is altered and the other where both hands are changed simultaneously by the application of the rubato. It is helpful to sing the melodic line, as this will provide some indication as to where the rubato could be applied.
Always approach the application of rubato to a piece of music with a ‘less is more’ attitude. It must be subtly applied, planned yet sound spontaneous.
The player needs to know the piece very well using the correct tempo with no rubato applied. Obviously using a metronome is extremely useful for this. It is advisable for the player to count as they play when deciding where to apply any rubato, as they will notice what effect this makes to the music.
There is a danger that when applying rubato that only an easing of the tempo is applied rather than an acceleration. In addition to this, the performer may not always return to the original tempo of the piece after an easing of the tempo is applied, thus meaning that the piece gradually becomes slower.
So, for most of the time the performer must ensure that any easing of the tempo is balanced by the application of an acceleration of the tempo, or vice versa.
There are exceptions however, if a composer has asked that the performer to play with animato or ritardando for example, these must be observed. Nevertheless, the performer should ask themselves why the composer has inserted these directions into the music and the effect they will have on the character of the piece.
Clearly the Musical Period, character and style of a piece will determine the level of rubato applied in a piece.
Generally speaking the performer should slow at the end of the piece, although of course this will depend on the character, style and Musical Period of the piece. When applying a ritardano at the end of the piece the performer must be careful to ensure that the last notes of the piece are not doubled in time value.
And in most cases, it would be advisable for the performer to wait until after the beginning of the piece before applying rubato, as it is best for the beat to be firmly established first.
The performer should be careful when applying rubato that it does note become predictable. If for example, the performer accelerates and eases the tempo at exactly the same point in the phrases of a piece it will become predictable and therefore will loose its effect.
By TheClassicalMusicGuy - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=102161592
The performer must be careful to ensure that the overall beat of a piece can be recognised.
There are instances where a composer has ‘written in’ some rubato to a certain extent. Examples of this are where notes at the end of a phrase are longer in rhythmic value than earlier in a phrase. Also, the performer should consider the reason why a composer has written rests or even a whole bar rest as these in themselves provide the music with an easing of the tempo to a certain degree.
The aspects in Classical music that a performer could consider applying rubato are - strong beats, appoggiaturas, dissonant intervals, syncopated notes, modulation notes, high or low notes in the melodic structure and those notes that are important to the harmony.
And, the following are some ideas as to where rubato could be applied in general - a change in harmony, key, mood, melodic material or a an unexpected dissonant note, the end of a phrase where it uses the tonic note of the piece, a ‘reach’ to a higher or lower note, any notes are chords that need to be highlighted, the main point of the piece or a change in the melodic material when a particular part is repeated.