Seventh Inning Stretch

In a previous blog, I explained stretch tuning. Here, I go into more detail on it's application.

Most people assume piano tuning is simple: each note is tuned to an exact mathematical frequency and everything lines up perfectly. That would be true... if piano strings behaved like perfect theoretical objects created in a physics lab by emotionally unavailable robots.

Unfortunately, pianos are built from steel, wood, felt, tension, age, humidity, and decades of accumulated personality disorders.

Real piano strings have stiffness. Because of this, their overtones do not line up perfectly with pure mathematical ratios. Instead, the overtones drift increasingly sharp as they rise. This phenomenon is called inharmonicity.

If a tuner adjusted every note to strict electronic equal temperament frequencies with no compensation, the piano would technically measure “correct” while sounding strangely lifeless and narrow to the human ear. Octaves would not bloom naturally. The instrument would feel compressed.

So piano tuners compensate.

This process is called stretch tuning.

In a stretched tuning:

• Bass notes are tuned slightly flat

• Treble notes are tuned increasingly sharp

• The temperament region near the middle of the piano stays closest to theoretical equal temperament

This creates a gradual widening, or “stretch,” across the keyboard... Ironically, making a piano sound properly in tune requires deliberately moving away from mathematically perfect tuning. Piano tuning lives in that strange territory where the ear often outranks the calculator.

The amount of stretch varies from piano to piano. Larger, high-end instruments like concert grands often allow for a smooth, refined stretch, while smaller uprights and spinets may require more careful compromise due to shorter strings and greater inharmonicity.

Contrary to popular belief, stretch tuning is not reserved only for luxury pianos. Nearly all pianos receive some degree of stretch tuning. The difference lies in how aggressively the stretch can be applied before the instrument begins to sound unstable or strained.

This sometimes leads to confusion among piano owners. While we do a degree of "stretching with the average piano, it's never referred to as a stretch tuning. Because the stretch is wider and more refined on high end pianos, the stretch tuning term is applied.

Older or lower-end pianos can occasionally struggle during major pitch raises because aging strings and structural wear make them less stable under changing tension. However, that is different from ordinary stretch tuning itself. The actual pitch adjustments involved in stretch tuning are relatively small, measured in cents rather than large jumps in pitch.

Modern electronic tuning devices account for stretch by calculating custom tuning curves for each piano. Even then, experienced tuners still rely heavily on the ear because software cannot fully predict how a piano wants to resonate in a real room under real playing conditions.

A skilled tuner learns to balance mathematics, string behavior, and the personality of the piano itself.

Because music is not just math.

It is math filtered through wood, steel, physics, craftsmanship, and human perception until something emotionally meaningful emerges from the chaos. Which is honestly more effort than most people put into their relationships.