Basic Operation
The Chord VCO 102 is similar to the VCO 101 and VCO 105 except that this VCO
contains 4 individual VCOs that are controlled in such a way as to produce
preset chords.
As with any analogue VCO, they are not precise unlike their digital equivalents
but this is often viewed as an advantage. Tuning 4 VCOs to produce chords and
keeping them in tune is not so easy. The 102 VCOs each have built in
temperature compensation but also have automatic tuning. The automatic
tuning is manually initiated and carried out by a microprocessor. The
microprocessor will tune each VCO over the entire range of an 88-note piano.
Tuning is close to ideal but not absolute to retain a beat frequency between
the VCOs.
To initiate an auto-tune, hold down the auto-tune button, the Status LED goes
out, when the LED comes back on, release the button. Tuning will then
commence and during this time, the paraphonic output will be muted. Once
tuning is complete, the Chord VCO will resume normal operation. Note: ensure
the external FM modulation input is disconnected.
It is possible to hear the tuning taking place if you so desire. Initiate the auto-
tune as above but rather than release the button when the LED comes back on,
keep the button pressed until the LED once again goes off. The paraphonic
output will no longer be muted and you will be able to monitor the output and
hear the frequencies change as they are tuned 1 octave at a time.
The chord selector switch allows any one of 16 preset chords, the chords are:
{4,7,0}, Major
{3,7,0}, Minor
{3,6,0}, Dimished
{4,8,0}, Augmented Major
{4,7,11}, Major 7th
{4,7,10}, Dominant 7th
{3,7,10}, Minor 7th
{3,6,10}, Minor 7th Flat 5th
{4,7,9}, Major 6th
