We have already learned that the normal voice leading behaviour of the leading note is to rise by step, if the chord progression is V-I, and that in a 4-part SATB piece, the leading note can move to the dominant, if it is in one of the two inner parts: the alto or the tenor.

In piano compositions, leading notes can sometimes move in other ways, but there will always be a good reason if they are not moving to the tonic or inner dominant.

Let’s look at how the leading notes behave in the opening of the second movement of Mozart’s Piano Sonata K570. The key is Eb major.

Mozart K570 voice leading

In bars 1 and 3, the leading note D rises to Eb in the following tonic chord, in the expected way.

In bar 2, the leading note D does not move to the tonic or to the dominant. Instead, at this point, the first four notes of the melody are shifted up an octave, and the harmony is changed to the first inversion tonic chord. If Mozart had resolved the D to Eb, it would result in another root position chord here, but the slight alteration to the first inversion is much more interesting.

The unresolved leading note is fine, because there is a very clear break in the melody where the range moves into the higher register, so the flow is already broken.

In bar 4, Mozart chose to resolve the D to Eb, instead of letting it fall to the dominant, even though it is the inner part. The effect is a gentle chord, which sounds lighter than a four-part chord.

In fact, in most piano music the leading note rises to the tonic whichever part it’s found in, whereas in vocal and instrumental music, inner parts often fall to the dominant. It’s quite interesting to discover why this is so.

If you play a very low note on an acoustic piano and let it die away, you will notice, as the sound diminishes, that a higher pitched 5th is audible. Try it on the 2nd lowest C – you should be able to hear a G- you can even “catch” the G on the pedal if you press the low C hard then quickly put the sustain pedal down immediately after). You may even be able to pick out the 3rd if you listen hard enough.

All acoustic pianos produce something called “sympathetic vibrations”. When you press a piano key, the wobbling string vibrates the air to make a sound. The vibrations in the air make some of the other higher strings on the piano vibrate as well, if the sustain pedal is pressed, and if they vibrate hard enough, you will hear them. Strings that have similar wave patterns will produce the strongest, and loudest, vibrations.

These whispery notes are called “overtones”. Even without pressing the pedal we can hear overtones in low notes, because their soundwaves are complex and include waves of higher up notes embedded within them.

The loudest overtone is the note an octave higher, but we tend not to notice it so easily as it blends in. The next loudest is a compound 5th higher, then compound major 3rd.

In a piano chord with a doubled root, a third, and no 5th, the overtones of a 5th are so strong, that there is no need to actually write a 5th into the chord, and in fact, including the 5th might make the chord sound a bit unbalanced (the 5ths would be too loud).

Although all instruments have overtones in their sounds, most of the overtones are nowhere near as audible as those on the piano (unless the player chooses to bring them out, for example a violinist can play “harmonics” or overtones by choice).