Dupflex Scales

Part Desciption:

1. Plate String with Front Bearing

2. Front Dupflex Scale

3. Capo d’astro bar

4. Anti-node; loop

5. Node

6. Soundboard

7. Bridge Pin

8. Bridge

9. Rear Dupflex Scale

10. Plate string with rear bearing; aliquot

11. Plate

12. Hitch Pin

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Pianos including a duplex scale portion were first introduced to the piano industry in the latter half of the nineteenth century. The purpose of the duplex scale is to enhance the quality of piano tone by regulating segments of the so-called non-speaking portion of the piano strings so that the vibrations of such regulated segments are in harmony with the vibrations of the so-called speaking length of the strings.

By adjusting the position of the movable frets of the duplex scales, the secondary portions of certain strings may be brought in harmony with the main length of the strings, improving the purity and fullness of the tone of the instrument.

However, no special tools or methods have been developed to tune the duplex scale. Although many pianos are equipped with movable fret bases which permit the adjustment of the length of a duplex scale portion, few companies or technicians have taken the time or trouble to make the fine adjustments necessary to tune the duplex scale.

Several reasons may help explain this technical impasse. First, the factory production procedures have apparently been trimmed by attrition since the flourishing days of the late nineteenth and early twentieth centuries, and the extra job of tuning the duplex scales has been either cut or assigned to other technicians who may not be sufficiently skilled in tuning. Second, in many instances the movable fret bases are difficult to move once the strings are set above them due to the extreme down-bearing pressure caused by the tension of the strings. Third, the construction of the movable fret bases themselves provide little if any means to assist in the fine adjustment procedure.

As a result of the foregoing and other difficulties, the practice of tuning the duplex scale portion of piano strings has been almost abandoned and any benefits that could be derived from its use severely curtailed. The original method of inserting a screwdriver blade against one of the protruding frets continues to be the only means available. This method is not only difficult and inefficient, it has serious drawbacks which include possible defacing and damaging the frets as well as scarring the underlying plate on which a fret base is supported. The use of a screwdriver for moving a fret base is both time consuming and imprecise, requiring substantial readjustment.