Why is a passing note easier to sing when descending than ascending?

Question

It seems to me that, when singing a linear three-note figure with a quick passing note, it is much easier to articulate the passing note when the figure is falling than rising, and I'd like to know why.

To see what I mean, try these at 90 BPM, 120 BPM, and 140 BPM, with legato in the voice:

In Early Medieval chant manuscripts (semi-improvised vocal music), it happens more often than not that the passing note is replaced by a slide or Schleifer or glissando. Rhythmically it is the same performance, except the passing note is not distinct.

But this happens only when ascending, never when descending: Not only is the slide symbol (the medieval quilisma) found almost exclusively in rising passages (except in a handful of manuscripts like the Montpellier H codex), but in other ornament-less manuscripts those same rising passages often have no passing note, while the corresponding falling passages almost always do.

This makes sense to me, for it feels a bit harder for the human voice to articulate a passing note when ascending, and easier to blur it into a portamento-like glide.

This difference in ease is perhaps clearer in rapid stepwise lines. Try singing these between 180 BPM and 200 BPM with legato in the voice, and you'll see that falling is slightly easier to pull off than rising, without blurring the passing notes:

But why is this? Is there some physio-acoustic difference concerning tightening the vocal cords or sharpening the soundwave that translates well to the practicality of distinguishing the passing notes versus eliding them?

Answer 1

The vibration of your vocal chords is what creates sound when you’re singing. The more quickly your vocal cords vibrate, the higher the pitch of the produced note. It requires less energy to slow down than to speed up (to a point).

Think of it this way: if you are jogging at a leisurely pace, which requires more energy—jogging slower or jogging more quickly? It’s really a physics question specifically dealing with kinetic energy.

Because the amount of energy required to hit the right pitches decreases in a descending musical figure, it is easier to be more accurate. In an ascending figure, the amount of energy required increases and is therefore more difficult to perform accurately.

I should also add that it also takes more energy to increase in volume because volume is proportional to the velocity of air as it travels through your vocal cords. When we emphasize a vowel, we increased the air speed subtly and briefly to stress that vowel. When we perform glottal stops or articulate certain consonant sounds, we momentarily stop the vibration of the vocal cords altogether, which takes a lot of energy. (Back to the running analogy, what takes more energy—sprinting 100 meters, or sprinting for ten meters, then abruptly stopping, then sprinting again for ten meters, repeated ten times?) You can feel this starting and stopping by gently pushing your fingers against your neck while singing “kakakakaka...” repeatedly.

So if we consider the combination of these two ideas (energy use when controlling pitch and energy use controlling volume), it’s easy to see why it is more difficult to articulate an ascending line (amount of energy increases while stopping and resuming vibrations in the vocal cords) than a descending line (amount of energy decreases while stopping and resuming vibrations).