| 摘要 |
A monophonic system includes means for voicing only tones derived in response to depression of a key associated with the highest pitched note when several keys are struck at approximately the same time, regardless of the order in which the keys are struck. If several keys are released at approximately the same time, only the tones derived in response to the highest remaining activated key are voiced, regardless of the release sequence. In response to the system being played legatissimo, voiced tones gradually shift in frequency, i.e., portamento is achieved. In response to the system being played staccatissimo, voiced tones shift in frequency in discrete steps. For unusual or special effect tone simulation, square wave tone signals derived from a frequency divider chain responsive to a voltage controlled oscillator, controlled primarily by the nomenclature of the highest pitch struck key, may be converted into a sawtooth waveform, a pulse waveform having a pulse width controlled by the highest pitch struck key, or can be left unaltered. Clicks and noise can be derived in response to key activations. The sawtooth, pulse, square wave, clicks and noise are fed through a filter selectively having band pass, low pass and high pass transfer characteristics that can be controlled with regard to resonant frequency and selectivity (Q) to provide additional unusual effects. A first group of tone signals derived from the frequency divider is processed to simulate flutes while a second group is processed to simulate brasses. In flute simulation, filtering of harmonics and passage to an output of the fundamental of the tone associated with the highest pitch struck key is assured by including in cascade a low pass filter and an amplifier having a variable gain characteristic directly related to the nomenclature of the highest pitch struck key. In brass simulation, an attack envelope having plural slopes is provided. Brass brightness is controlled by providing a variable wave shaper that responds to pedal control or is a transient function during the attack of the voice. Flatting during the attack of a brass tone is simulated by transiently reducing the voltage controlled oscillator frequency when a new highest pitch key is struck by an amount indicative of the nomenclature of the struck key. Attack rates of the flutes and unusual tones can be controlled to a plurality of values; if the system is in a percussive mode the attack rate is relatively fast. Roll-off rate of certain flute tones is fixed, while other flute tones and the unusual tones can be provided with a fixed roll-off or sustain effect. The voltage controlled oscillator frequency is modulated by a vibrato oscillator frequency, the frequency of which can be fixed or controlled in a random manner in response to a noise source to simulate brass vibrato effects.
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