Can We Actually Measure Inner Hearing?

How do you measure a sound that only one person can hear?

How do we know what another pianist hears before playing?

It seems almost impossible.

I can ask you to look at a score and hear the opening phrase inwardly. You can close your eyes and tell me that you hear it perfectly clearly.

But I cannot enter your experience.

Perhaps you hear every pitch precisely. Perhaps you sense only the contour of the melody. Perhaps the pitches are clear but the harmony is vague. Perhaps you hear the melody but not the inner voices. Perhaps the sound has no particular timbre. Perhaps you experience something remarkably close to an actual performance.

From the outside, all of these experiences may receive the same answer:

"Yes, I can hear it."

This is one of the fundamental difficulties facing research into auditory imagery. The experience is internal, yet science needs something observable.

And researchers have found an ingenious way of approaching the problem.

How do you test a sound nobody else can hear?

In 2020, Rebecca Gelding, Peter Harrison and their colleagues published an adaptive test of auditory mental imagery called the aPIAT — the adaptive Pitch Imagery Arrow Task.

Its purpose was very specific: to measure a person's ability to maintain and manipulate imagined pitch without depending simply on self-report.

The principle is rather elegant.

A participant first hears a musical scale establishing a tonal context and a starting pitch. Arrows then indicate movements up or down through that scale. At a certain point, the sound disappears — but the arrows continue.

The participant now has to continue the pitch sequence internally.

At the end, an actual note is played. The participant decides whether it corresponds to the pitch they should have reached in imagination.

There is therefore a correct or incorrect answer.

The invisible experience has produced a measurable consequence.

The adaptive version takes about eight minutes and adjusts its difficulty to the ability of the individual participant. The authors' analysis suggests that success depends particularly on maintaining and manipulating imagined tones while resisting perceptual biases that could interfere with the answer.

This is a clever solution to a difficult problem.

But what fascinated me most was not what the test measures.

It was what the researchers deliberately remove.

To measure pitch, first remove the music

If you want to know whether someone can manipulate an imagined pitch, you cannot allow too many other variables to interfere.

So the task controls musical features such as rhythm, timbre and harmony in order to isolate pitch imagery.

Scientifically, this makes perfect sense.

Musical imagery is complicated. If pitch, rhythm, harmony, timbre, memory, notation and movement are all involved simultaneously, it becomes very difficult to know which ability produced the result.

To measure one thing clearly, we simplify.

But a pianist eventually faces the opposite problem.

We have to put everything back.

And this is where the question of measuring inner hearing becomes much more complicated.

What do we mean by "I hear the score"?

Imagine two pianists looking silently at the same passage.

Both can accurately imagine its pitches.

Are their internal experiences therefore equally developed?

Not necessarily.

• One may hear the melody accurately but have only a vague impression of the accompanying voices. The other may experience each voice independently.
• One may imagine the correct notes without a particular quality of sound. The other may experience a specific tonal colour.
• One may know intellectually that the harmony has changed. The other may hear the notes within the changed harmony before touching the instrument.

Dynamics may be another layer. Voicing another. The duration of longer notes within polyphonic texture another. And movement may already be present in the experience as well.

So perhaps the question is not simply:

How vivid is your musical imagery?

It may also be:

What is actually inside it?

The Gelding and Harrison paper itself acknowledges that musical imagery — particularly in musicians — can extend beyond the auditory modality, into multimodal representations involving notation and bodily movement.

I used to hear almost nothing

This question is very personal to me, because I remember what it was like to have extremely weak inner hearing.

I was already receiving professional musical education. I could learn repertoire, perform publicly and participate successfully in competitions.

Yet if I looked at notation, the internal sound was remarkably limited.

Over many years, I deliberately worked on changing this.

What surprised me was that inner hearing did not seem to develop as one single ability that simply became "stronger."

Different dimensions had to be discovered.

First, an individual note could acquire a specific imagined sound. Then that sound could acquire texture and movement. Several notes could gradually be experienced together. Harmony could become something heard rather than merely understood. Dynamics and voicing could become part of the imagined sound before playing.

And alongside sound imagination, another process developed: inner singing — the continuous experience between notes through glissando and resistance.

That progression has made me increasingly cautious about the phrase "good inner hearing."

It may conceal more than it reveals.

Could two pianists hear completely different things?

Suppose we could test two pianists and establish that both have excellent pitch-imagery ability.

Then we give them an unfamiliar polyphonic score.

• Could both internally hear every written pitch?
• Could they maintain the duration of sustained notes while other voices continue?
• Could they hear each voice independently?
• Could they change the imagined voicing deliberately?
• Could they imagine the same passage first piano, then forte, without changing its other qualities?
• Could they hear the harmonic colour of each event?
• Could they imagine a particular sound texture?
• And could they experience the movement connected with that sound before physically playing it?

These are not questions answered by the aPIAT — and they are not supposed to be. The test was designed precisely to avoid this complexity. It isolates pitch because isolation makes measurement possible.

But once we return to actual musicianship, the complexity becomes the interesting part.

Perhaps inner hearing needs a profile, not a score

This makes me wonder whether a sufficiently developed measurement of musical imagery might eventually look less like a single scale from weak to strong, and more like a profile.

A pianist might possess excellent pitch imagery but relatively indistinct timbral imagery. Another might experience melody and harmony vividly but struggle to maintain independent polyphonic voices. Another might have a powerful internal sound but little accompanying sense of movement.

And these capacities may not necessarily develop together.

I do not know whether the particular distinctions I observe pedagogically correspond to scientifically separable imagery capacities. That would require experimental investigation.

But the measurement problem itself is fascinating.

Because once we begin asking what a pianist actually experiences internally, vividness alone may not be enough.

A photograph can be extremely vivid and still contain very little.

The same may be true of an imagined sound.

And then there is movement

There is another reason why measurement becomes difficult.

For me, increasingly developed sound imagination did not remain exclusively auditory.

Movement became connected with it.

When sound texture is imagined in my practice, sound movement accompanies it. Inner singing connects consecutive notes. At the instrument, sound imagination becomes related to the motion of the hand, while intonation becomes connected with arm weight and articulation. Later, harmony, dynamics and voicing are added to that imagined representation.

The distinction between "hearing" and "moving" therefore becomes less clear than it first appears.

This is also why the paper's acknowledgment of multimodal musical imagery interests me so much. Its test isolates auditory pitch for a good scientific reason. But the musical experience of an instrumentalist may eventually become an interaction between auditory, visual and bodily representations.

Perhaps advanced inner hearing is not simply an increasingly accurate recording playing inside the head.

Perhaps it becomes an increasingly organized internal musical event.

So can we measure inner hearing?

Yes — but only if we are very precise about what we mean by inner hearing.

We can devise behavioural tasks that tell us something objective about whether a person can maintain and manipulate imagined pitch. The aPIAT is an elegant example, and, importantly, it works across people with different levels of musical background.

But the moment we ask what a pianist experiences while silently reading an actual score, the question expands.

Pitch is only the beginning.

There may be rhythm, timbre, harmony, dynamics, voicing, polyphony, sound movement, notation and bodily representation — each interacting with the others.

And perhaps this leads to an even more interesting question than whether inner hearing can be measured:

If these dimensions can be developed separately, could we measure a pianist while the internal musical representation itself is changing?

Not simply before and after years of musical education. But during the process.

• Could we watch an imagined note acquire timbre?
• Could we observe the point at which harmony becomes internally audible rather than analytically understood?
• Could we measure the development from hearing a melodic line to maintaining several voices simultaneously?
• Could we detect a changing relationship between imagined sound and imagined movement?

The aPIAT shows something important: an experience that seems entirely private can leave behavioural traces that science can measure.

Perhaps the next challenge is not merely to measure how strongly musicians imagine.

It is to understand what their inner music has learned to contain.