A piece may contain all the correct notes and still not be played rhythmically. It can happen that the note is early or the note is late; a rest may be omitted. This happens because the hands try to dictate the time, and while fingers have an excellent way of executing this action, their ability to keep track of beats is not the same.
The voice is a great resource because of the way that vocalizing the counts externalizes time outside of the hands. If you vocalize “one and two and” while playing, your notes will be compelled to remain within that metronomic time. It is easier to detect the difference between a quarter and a half note when you hear the gap. Your voice becomes a simple metronome which can enable your hands to stop guessing the time.
Here’s the drill before you even get to the keys: look at the single measure of music, beat the measure on your knees and vocalize the beats out loud evenly. For example, if there are quarter notes, each quarter note will get “one.” If it is half notes, then tap the beat twice and then release, or count them through two vocal counts while singing. If you hear a rest, keep counting and vocalizing even when you do not play it. The rhythm has been pre-studied while the fingers have been learning to perform a different task.
Once you go back to your piano or digital piano and start playing with one hand, try a short phrase, perhaps two measures. Slow down your playing speed. When you play, vocalize the beats out loud. If the voice is unable to follow as your hands get slower, the tempo will not be even. Slow it down even more until your hands do not have to tighten their shoulders or grip.
The downside is that vocalizing is awkward. Some students find that they mumble and count in a hush, or they count in the back of their head as it is considered distracting. However, when the tempo picks up or the notes become more difficult, silent vocalizing is very likely to go away. Vocalizing does not sound nice; it is a way for you to figure out what your rhythm is.
Once your vocalization becomes comfortable, a metronome can be used as a guide, but it should not be your guide. If you are not entirely sure where your notes will land when your metronome clicks, your metronome will sound more like stress and not a beat. By vocalizing before, you know what your rhythm looks like when the metronome clicks. When your rhythm is more solid, a metronome can be set, and it can be slow enough to be a guide.
You will hear this as control of your pauses as you will not pause after a mistake, but you will return to the beat and count off on the next beat. If you play fast through the easy measures, it will not slow down through the more difficult sections because you will be able to tell where the beat is off. This is not the perfect way to play, but it will help your hands be more in sync as they know where the note and rest and measure begin.