Why Lower the Tenor Partial Change in an FAC Tuning?

Understanding Partial-Change Errors

Any partial change in a tuning system can introduce a small error at the point where the partial change occurs. Those errors can affect the accuracy, consistency, and reliability of the overall tuning. By locating and correcting partial-change errors, technicians can produce a more precise and dependable aural result.

Creating a Smoother A2–A4 Temperament Range

A smoother, more consistent temperament across the A2–A4 range is easier to achieve when every note in that span uses the same partial. Using one harmonic reference throughout the range removes the opportunity for partial-change errors within the temperament.

Most tuning systems introduce at least one partial change between A2 and A4; some include two or even three. Each change creates a potential error point, which can lead to uneven interval beating and aural inconsistencies. This is especially important in the lower half of the piano, where reliable aural checks are essential.

The Tenor Partial Change in an FAC Tuning

In an FAC tuning, there is only one partial change within the A2–A4 range. By default, the tenor partial change occurs between B2 and C3. Standard FAC tunings use the 4th partial from C3 through B4 and the 6th partial from B2 down to A0.

Moving that partial change point down—from B2/C3 to G#2/A2—improves consistency in the tenor and makes the rest of the bass more reliable. Because FAC tunings have no additional partial changes below the tenor change, lowering this point helps remove a significant source of potential error.

Other tuning systems may include additional partial changes lower in the bass, below A2. Each one carries with it its own potential error, which can become especially problematic on smaller-scale pianos with shorter strings.  Those ‘extra’ partial changes and their errors, can cause big issues for bass tuning on the shorter scale pianos.

Optimizing the Two-Octave Temperament Range

To establish a full two-octave A2–A4 temperament range using only 4th partials, move the partial change from B2/C3 down to G#2/A2. With this adjustment, every note from A2 through A4 is tuned from its 4th partial, creating a seamless and uniform reference across the entire two-octave span.

Improving the Reliability of Aural Checks

Lowering the tenor partial change from B2/C3 to G#2/A2 removes partial-change inconsistencies from the A2–A4 range. As a result, aural checks become more dependable because they are no longer affected by errors introduced at partial-change points.

The A2–A4 area often contains several built-in scaling challenges. On all but the largest pianos, this range may include:

  • The break between the long bridge and the bass bridge
  • The transition from plain wire to wound bichords
  • In many cases, the change from plain-wire trichords to wound bichords
  • In other cases, the change from plain-wire bichords to wound bichords

These scaling issues are inherent to the piano’s design. A technician cannot remove or remedy them, but the technician can avoid adding or leaving unnecessary partial-change errors in the tuning.

Lowering the tenor partial change from B2/C3 to G#2/A2 is a simple adjustment that helps reduce those errors and improves the reliability of the tuning checks in this range.

The Technician’s Role

Technicians should know where partial changes occur in the tuning system they are using. They should also be prepared to recognize and correct the “hiccups” or inconsistencies that can appear when partial-change errors occur.