Combined tone generation on a single keyboard for an electronic musical instrument

DETAILED DESCRIPTION In a Polyphonic Tone Synthesizer of the type described in U.
S.
Pat.
No.
4,085,644 a computation cycle and a data transfer cycle are repetitively and independently implemented to provide data which are converted to musical waveshapes.
A sequence of computation cycles is implemented during each of which a first master data set is created using a first set of harmonic coefficients which are selected by a first set actuated tone switches.
At the end of each computation cycle, the computed first master data set is stored in a main register.
Simultaneously with the computation of the first master data set, a second master data set is created using a second set of harmonic coefficients which may be time variant in magnitude.
At the end of each computation cycle, the computed master data set is stored in a formant register.
Following each individual computation cycle, a transfer cycle is initiated during which the stored first master data set is transferred to a note register which is an element of each of a number of tone generators.
The tone generators are assigned to actuated keyboard switches.
A high note detector is used to detect the keyswitch corresponding to the current highest actuated note.
The output from the high note detector is used to inhibit a transfer of the first master data set to a tone generator corresponding to the highest frequency note.
The stored second master data set in response to the high note detector is transferred during the transfer cycle to a tone generator which is assigned to the highest frequency note.
The data stored in the note registers is sequentially and repetitively read out to a digital-to-analog converter at a rate corresponding to the fundamental frequency associated with its assigned actuated keyboard switch.
The output tone generator continues uninterrupted during the computation and transfer cycles.
An object of the present invention is to provide a means for imitating the action of the combination of a conventional instrument keyboard in combination with a monophonic synthesizer imbedded in a tone generator system in which the number of tone generators is less than the number of keyswitches