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The Arpopone desktop
Overview
The Arpopone AKA HARP'O'PHONE is a
melody/bass line generator with a chord and rhythmic
section, available in desktop and euro rack
format.
It is based on analog ramp divider,
similar to those used for the Multicassa which are inspired
to Oskar
Sala's Mixtur Trautonium,
an early electronic musical instrument.
Each divider generates a voltage ramp
starting from a master clock (internal or
external)
a potentiometer is used to set the
number of steps and thus the division ratio with a minimum of
1.
There are ten of such divider in the
different sections of the instrument:
- 2 for the rhythmic section (trigger
pulses 1 and 2)
- 2 for the scale generator, these have a ramp output that forms
the melody line
- 6 for the audio dividers, the 2 prescalers are chained with 4
note dividers, one for bass and 3 for
chords
A further divider comes into play if
external clock is selected, in this case the BPM control acts as a
clock divider making possible the synchronization with other
instruments (at maximum speed divider=1
Specification :
CLOCK GENERATOR
BPM : Set the speed of master clock
or the external clock divider (RED led)
EXT-INT: select internal clock (set
by BPM) or external clock (via the EXT CLOCK IN) the EXT CLOCK OUT
pulses are synchronous with the RED led flashes.
The Apopone accepts any
type of clock pulse or square wave of 3/12 volts amplitude, with
any polarity including the Midi clock (with custom
cable) as long as in the midi bit line is present only
midi clock message and no other messages like, notes,
control changes, sysex, etc.
When in external clock,
tempo pot. works as clock divider for the incoming clock in
pulse, this is useful for divide fast clock like midi or synch
24 for slow clock like Korg volca series keep the divider to
1, tempo pot to max.
TRIGGER
GENERATOR
TRIG1 TRIG2 : set how many clock
pulses are needed to flash the GREEN and YELLOW
led
DIVIDERS : the two trigger output are
the rhythmic section of the instrument and are used for playing
notes and advance notes of the scale generators the division ratio
is 1 to around 40
TRIG MIX : selects a single trigger (1 or 2) or both (1+2) to
advance the scales the output of TRIG MIX is also fed to the
TRIGGER OUT
SCALE #STEP : Sets the number of steps for the two scale generators
that, added together by the SCALE MIXER will play the melody on the
VCO.
SCALE GENERATOR
The pulses selected with TRIG MIX are sent to two scale generators,
each scale generator outputs a voltage that increases in steps.
The brightness of the two led's (WHITE and BLUE) are proportional
to the output voltage giving an indication of the current position
in the scale.
The number of steps is set by the two #STEP controls from a
minimum of 1 to around 40.
SCALE MIXER
In the mixer section the two scale are summed together to obtain a
more complex pattern, the amount of each scale can be set by two
controls and can be positive (ascending scale) or negative
(descending scale).
In center position the amount is 0
(steady note) an OFFSET control set the minimum voltage and hence
the lowest note that can be played.
Be aware that these are NOT tempered scales, all micro intervals
are possible
fine tuning of the melody being played is done with these three
scale mixer controls.
VCO
The notes are played by the vco, the VCO PITCH transposes the
melody maintaining the same interval between notes, as set through
the SCALE MIXER.
DIVIDER SECTION
The note generated by the VCO is fed to a chain of dividers to
obtain 4 sub harmonics of the original note, one of these is the
bass section with its own filter and envelope, the other three form
the chord section with their envelope.
Each divider is similar to the
trigger dividers with the difference that it acts on notes and not
on rhythms generating a subharmonic
sequence:
for example if the note produced by
the VCO is C4 the output will be:
(rotating from left to right) C4,C3,F2,C2,Ab1,F1,D1(not
really),C1,Bb0...
Two prescalers are used, each of them is chained with two dividers
that further divide the note, the same way many types of chords can
be generated by setting the proper dividers each single divider can
be played separately by means of the four buttons in the
MANUAL PLAY section one for the bass the other three for each note
that form the chord (CH1,CH2,CH3)
ENVELOPE SECTION
The two envelope section are identical, both have a selector for
different trigger sources :
-TRIG1 & TRIG2 the envelope
starts at the flash of the GREEN LED (bass) or YELLOW LED
(chord)
-SB1 & SB2 the envelope starts at the first step of
SCALE1 (bass) or SCALE2 (chord)
-White & Blue the envelope
follows the intensity of the WHITE LED (bass) or the BLUE LED
(chord) except for this setting the envelope length is set by
the two controls BASS ENV and CHORD ENV an EXT CV input allows to
provide an external envelope to drive the
VCA.
BASS FILTER
The bass channel is passed through a resonant low pass filter with
CUTOFF and RESONANCE control.
OUT MIXER
Finally the two channels BASS and CHORD are mixed together, the
output level is set by the BASS LEV and CHORD LEV controls.
Two outputs jacks are present: the mono OUT jack on the back panel
and the STEREO jack on the front panel useful for listening with
phones and for separate channel out.
POWER INPUT
Power also non-stabilized 12 volts
with + central tip There
are two power inputs, one can be used for power link another device
with custom cable.
A SIMPLE BEGINNER'S
TUTORIAL
Connect power (12 V.) and an amplifier or headphones
Select internal clock (EXT-INT switch) and BPM to your favorite
rate (RED flashes)
Start with all the controls to mid position
Move TRIG1 and TRIG2 to the left position (counterclockwise) :
GREEN and YELLOW will flash at the same rate as RED.
Select TRIG1 and TRIG2 on ENVELOPE SELECTOR switches (down
position)
you'll hear two distinct sound (left and right if you are
stereo) at the time GREEN and YELLOW flash
Slowly raise TRIG1 or TRIG2: the sound and flashes will slow down
always in sync with RED flashes
Let's work on sound : adjust BASS ENV, BASS LEV, CUTOFF and
RESONANCE for nicest bass the chord section may need to adjust CH1
CH2 CH3 (start with all at left position) these control along with
PRESCALER allow to choose the notes the chord is made of the MANUAL
PLAY buttons allow to listen the separate notes, you can stop the
clock (EXT position) and try different combination of prescaler and
note divider, adjust VCO PITCH to transpose your chords
... if you care about harmony (musician mode ON)
You will notice that all PRESCALER and note dividers play the
highest note when in left position (divider=1) raising slowly one
of these controls will lead to a subharmonic sequence (frequency
divided by 2,3,4,ecc)
If the first note is for example C4
The sequence will be : C4 C3 F2 C2 Ab1 F1 ....
it's easy to get a minor chord setting the three chord dividers to
Ab1 C2 F2 you'll get a F minor and you can transpose it using
VCO PITCH.
Major chords are more tricky: set PRESCALER 1 to F2 and PRESCALER 2
to C2, transpose 2 octaves up CH1, will generate a sequence
starting from F4 F3 Bb2 F2 Db2 Bb1 ... (the original sequence
transposed one fourth up), CH2 and CH3 will play the original
sequence C4 C3 F2 C2 Ab1 F1 ...
Now pick a Ab1 Db2 F and you have a
major Db chord you can transpose as always with VCO PITCH more
other types of chord can be obtained this way (musician mode
OFF)
.... now the scale generators
Move one of the SCALE MIXER control: you hear a scale (=sequence of
notes) ascending (toward +) or descending (toward -), adjust the
number of step with the corresponding SCALE #STEP controls the two
scale generator can be mixed at every ratio and an OFFSET control
allows to tune the melody, you can still transpose it using VCO
PITCH.
Regarding VCO PITCH and OFFSET: it
may seem they do the same thing, but it's incorrect VCO PITCH
multiplies all frequencies by a fixed ratio and thus transposes a
melody leaving intervals unchanged OFFSET adds a fixed value
to all frequencies and so the melody sounds different from the
original.
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