Metal percussion generator

41 The objective of this circuit is to obtain a synthesizer-controlled equivalent sound as produced by such metal indefinite pitch per- cussion instruments as cymbals, gong, and anvil. Fig. 1 shows that the generator comprises four indepen- dently tuneable VCOs which supply rectangular output signals to a com- bination of XOR gates. One of four identical KOV (keyboard output voltage) driven VCOs is shown in Fig. 2. The use of fast opamp types ensures linear VCO operation well up to 4 kHz, while FET Ti improves upon the linearity of the voltage-frequency curve relevant to the combination of integrator and comparator. With the VCO con- structed four times over and connec- ted as shown in Fig. 1, drive controls Pl. . . P4 allow the user to set the out- put sound as desired. The outputs of buffer opamps Al . . A4 (IC1, Type TL084) should measure 0 V offset with the KOV rail grounded. If this can not be attained, the IC will have to be exchanged with a more stable type. Linearity of ea...