What Is Sympathetic Resonance?
It’s becoming a feature commonly seen on digital pianos, so here ask what is sympathetic resonance?
Digital pianos have evolved immeasurably in the past decade. Whereas the amount of sample RAM on early instruments meant that the piano sound was economically created by using a few, select samples of piano keys, and spreading them across the keyboard, modern pianos sample every key, and often at multiple velocities, too.
The result is a far more authentic recreation of an acoustic piano. These days, however, there are numerous features that recreate the sort of minute detail that many would overlook, but make a huge difference to the how ‘real’ a piano sounds. Pedal noise, un-looped decays, hammer noise- all have been included on some pianos.
Sympathetic resonance is one such feature – but what is sympathetic resonance?
To understand what sympathetic resonance does on a digital piano, we first need to consider how an acoustic piano works.
In it’s resting state (when no keys are pressed), the hammers on a piano rest on the strings, so that they make no sound.
When a key is pressed, the hammer hits the strings for that note. If the key is held down, the hammer will remain off the string, so that the note will sustain. Releasing the key will place the hammer back on the strings, deadening them.
With me so far? Good.
Often, when playing the piano, the music will involve a combination of longer notes and shorter notes simultaneously- a held chord, with a staccato melody over the top, for example.
When this happens the strings for the held notes will be open to sustain. The vibrations caused by the staccato notes causes the ‘open’ strings to vibrate according to the note played.
A Sympathetic Resonance feature recreates this effect on a digital piano.
Why is it desirable?
First and foremost, it makes playing a digital piano a far more authentic experience. Every note is made of multiple harmonics, however, and when a string resonates sympathetically, it is at the frequencies of shared harmonics.
The result is that it adds a richness that enhances the notes played, just as an acoustic piano does. It also removes the sense of every note being completely dry and separated, which some digital piano sounds can suffer from. Instead it adds a sort of sonic ‘glue’ that ties everything together as a single instrument, and makes it more natural sounding.
Most of the major digital piano brands incorporate this technology into their mid to high spec pianos. Roland’s SuperNATURAL technology and the Nord Piano 2 (and other Piano Library compatible instruments) provide great examples of how much this can add to a piano sound.
Damper resonance is closely related to sympathetic resonance. When the damper pedal is depressed, it stops the hammers from returning to rest on the strings so that the notes continue to sustain. So, when the damper pedal is down, all strings are free to vibrate.
This means that all strings will resonate sympathetically when any note is played.