Roland owner manual How the VK-8 Works, About the Virtual Tonewheel Sound Generator

How the VK-8 Works

About the Virtual Tonewheel Sound Generator

A traditional tone wheel organ produces the sound by 91 toothed wheels called “tone wheels.” Each tone wheel produces a different pitch. A motor is used to rotate these tone wheels past electromagnetic coils, and as the teeth of each wheel pass by the corresponding electromagnetic coil, an audio signal is generated. The combination of harmonic bars and the notes that are pressed then select the audio signals that are output, producing the sound of the organ.

The virtual tonewheel sound generator of the VK-8 uses digital technology to precisely re-create the sound- production mechanism of a tone wheel organ. The 91 toothed wheels are constantly “rotating” digitally, and are able to produce sound at any time. The sound produced by these virtual tonewheels is determined by the combination of harmonic bars and the state of the notes played on the keyboard—exactly as on traditional tone wheel organs.

How the Organ Sound are Created

Tone Wheels

Tone wheels rotate constantly, and will therefore “speak” the instant you play a note. The virtual tonewheel sound generator of the VK-8 is also producing sound constantly, allowing very rapid response when you play a note. This rapid response is especially valuable when you use characteristic organ performance techniques such as glissando.

The organ sound consists of a fundamental and eight harmonics, and these are mixed according to the combination of the harmonic bars. You can use the harmonic bars to modify the tone even while you play, allowing a high degree of expressive flexibility.

Percussion

Tone wheel percussion is used when you want to add an attack to the notes you play, making the sound more crisp. Relative to the pitch of the note you play, you can specify either the second (SECOND) or third (THIRD) partial as the pitch of the percussion sound, and you can decrease the percussion volume (SOFT) or lengthen its decay (SLOW).

The percussion on tone wheel organs is of a type called “single-trigger,” meaning that percussion was not applied to all the notes that were played, but only to the note that was pressed first. If you release the currently-played key(s), percussion will sound for the next-played note. If you play legato (with notes smoothly connected), percussion will be applied only to the first note, and not to subsequent notes. If you play staccato, percussion will be applied to all notes. If you play rapidly when using percussion, the percussion circuit may not keep up with your playing, causing the percussion sound to become softer. However, the VK- 8 allows you to adjust the speed of recovery so that it will keep up even with rapid playing (p. 51). On a tone wheel organ, the way in which percussion is applied is a very important element in enhancing the expressiveness of the performance.

On tone wheel organs, the 1' harmonic bar was used to produce the percussion sound. This means that when you add percussion, the sound of the 1' harmonic bar will no longer be heard. Also, percussion will be applied only to the Upper Part.

On tone wheel organs, turning off percussion [SOFT] button would lower the volume of the organ, but the VK-8 allows you to adjust it so the volume of the organ won’t change when percussion [SOFT] button is switched on/off (p. 51).

Key Click

The first generations of traditional tone wheel organs produced a “blip” noise (separately from percussion) when a note was pressed or released. Initially, this click noise was considered a problem, but blues and rock musicians came to utilize it in their performances, and the key click became an indispensable part of the organ sound in jazz as well.

On the VK-8 you can independently adjust the volume of the key click for key-on and key-off (p. 51).

13