Formant filter generator for an electronic musical instrument

An electronic musical instrument which combines harmonic components corresponding to respective harmonic orders into a desired musical waveform, the desired musical waveform having a formant filter characteristic with a harmonic order (q), a cut-off harmonic order (q.sub.c) which is below or above the harmonic order, a level (Ha), and a slope (SL), comprising:

• cut-off harmonic order (q.sub.c) variable setting means for generating the cut-off harmonic order (q.sub.c) which determines a cut-off position of the formant filter characteristic sacling the level of each harmonic component, the cut-off harmonic order (q.sub.c) being composed of an integral and a decimal part,
• level generating means for generating the level (Ha) of the formant filter characteristic;
• slope coefficient generating means for generating a slope coefficient which determines the slope of the formant filter characteristic;
• slope calculating means for receiving the generator slope coefficient, for accumulating the generated slope coefficient and for extracting the accumulated value from the decimal part of the cut-off harmonic order (q.sub.c), for calculating the slope (SL) of the formant filter characteristic;
• memory means for storing the calculated slope (SL), as the slope (SL) of the formant filter characteristic, at an address in the memory means;
• means for generating an address for reading out the slope (SL) from the memory means on the basis of the integral part of the cut-off harmonic order (q.sub.c) and the harmonic order (q);
• select means for selecting one of the level (Ha) from the level generating means and the slope (SL) from the memory means in accordance with the integral part of the cut-off harmonic order (q.sub.c), the select means generating a formant filter characteristic signal therefrom;
• and
• means for using the formant filter characteristic signal to control each harmonic component value.