Using the EVP88 Stretch Parameters

The EVP88 is tuned to an equal-tempered scale. You can deviate from this, however, and stretch the tuning in the bass and treble ranges—much as you can do with acoustic pianos (especially upright pianos). You can also modulate the tuning of each note randomly.

Figure. Stretch parameters.
  • Lower Stretch knob: Determines the amount of deviation from the equal-tempered scale—in the bass end of the sound. The higher the value, the farther down the low notes are tuned. At a setting of 0, the EVP88 is tuned to an equal-tempered scale, with each octave down halving the frequency.
  • Upper Stretch knob: Determines the amount of deviation from the equal-tempered scale-in the treble end of the sound. The higher the value, the farther up the high notes are tuned. At a setting of 0, the EVP88 is tuned to an equal-tempered scale, with each octave up doubling the frequency.
  • Warmth knob: Determines the amount of (random) deviation from an equal-tempered scale. Each note is slightly detuned from the next, adding life and richness to the sound (particularly when high Warmth values are selected).

    Note: Use of both Warmth and Upper or Lower Stretch may result in a detuned sound that is quite similar to a heavy chorus effect. In some instances, this effect may be so extreme that the EVP88 sounds out of tune with the rest of your project.

Stretch Tuning in Acoustic Instruments

The tones of upright pianos, and to a lesser extent grand pianos (due to their longer strings), have inharmonicities in their harmonic structure. This also applies to other stringed instruments, but it particularly affects pianos due to the length, density, and tension of the strings.

If a piano is perfectly tuned to equal temperament across the keyboard range, the overtones of the low strings and the fundamentals of the high strings will sound out of tune with each other. To circumvent this problem, piano tuners use a technique known as stretch tuning, where the high and low registers of the piano are tuned higher and lower, respectively. This results in the harmonics of the low strings being in tune with the fundamental tones of the upper strings. In essence, pianos are intentionally “out of tune” (from equal temperament), so that the lower and upper registers will sound in tune.

As electric pianos don’t have strings, this inharmonic relationship doesn’t apply to the EVP88, nor the original instruments it emulates. The stretch feature was primarily included for situations where you want to use the EVP88 in an arrangement alongside an acoustic piano recording.