Grasp the changes in tempo in piano songs by experimenting with its upper and lower limits, sensing the relative tempo of nearby phrases and singing mentally
The serene tempo of the phrase from Canon in D in which the 2 bars shown in Image 1 below occupy has been a joy to listen to. So much so I was drawn to learn the song on my own even though I was unsure if it was within my level of proficiency.
Yet in its serenity, I still sensed subtle changes in the tempo at certain intervals going from 1 bar to the next. It felt off when I changed the tempo on the first note of the bar. It sounded too sudden, not in harmony with the rest of the phrase. Example shown in Image 2 below.
Wondering that if it felt sudden, what is its opposite? How would it sound if instead of changing the tempo on the first note of the bar, the change began later in the bar? But identifying the exact note on which to do so was another puzzle.
Seldom does a mood to a music suddenly change at its climax, therefore the moment when the beat is weak had to be the correct moment to begin the change in tempo. I was proven right when I played as such.
Further consultation with more experienced pianist friends revealed that changes in tempo adhere to certain laws. For example, gradual change of tempo (ritardando, accelerando) and volume too (crescendo, diminuendo) are not allowed at the beginning of a phrase or bar, it is only allowed later and even then, only on a weak beat. Example shown in Image 2 below.
Developing one’s piano technique by practising actual compositions forces the student to become attentive to the nuances. As described above, subtle changes in tempo appeared clear to me. On the contrary, were I to practice dry as dust fingering exercises devoid of any artistic contents I would end up going through the motions for the sake of playing, not for the sake of music - although there are times such exercises serve a purpose, for example to warm-up, building finger strength and agility.
Practising an actual composition such as Canon in D, my intuition was heightened towards its requirement for playing so that the tone quality, tempo, nuances, and acceleration were clear. Tempo-wise, the requirements could be figured out through experimentation. Try playing the phrase as slow as possible, as fast as possible, and somewhere in between to establish its minimum and maximum limits.
Comparing the phrase’s tempo with another phrase nearby is also useful. Singing mentally the tempo set me up to harmonize my playing with the rhythmic mood, intent, and emotional content of the phrase. Resulting in accurately executed tempo during performance.
If the phrase is a long one. Break it into smaller sections, then take the steps described above. Practising single hands separately at first is the more effective way to learn a song. When ready to practise hands together, start the process of experimenting with the minimum and maximum tempo, sensing the relative tempo of other nearby phrases, and singing mentally.
Mistake in tempo distorts the whole performance. Although once the pianist regains his composure the tempo evens out in mid-performance, the unity has been lost. Therefore, remember to make changes in tempo later in a bar and never at the beginning. Make it so on a weak beat not at the climax of a phrase. The requirements to convey correct artistic image of a composition consisting of tone quality, tempo, nuances, and acceleration can be met through experimentation.