There is a lot of vocal like sounds in pop music and older rock that
comes from an analog style vocorder. The vocorder uses the different
bands, an 8 band vocorder for example, to alter any incoming synth signal.
The incoming voice signal is not mixed with the synth tone but is used
as a controller for the volume of each of the 8 bands. All that makes
those sounds "vocal" and distinguishable as words are the
filters. Another approach would be to make some strange voices by simply
controlling the volumes of those band pass filters independently.
A good way to control the exact volume of 4 or more voltage controlled
amplifiers that control the vocal sounds is to use midi to cv conversion
and have a computer control the midi. You may want to look at the soundblaster
midi diagram if you don't have a good midi setup. Cakewalk, a midi computer
program with many versions, seems to work well for this.
Think about how the vocorder works when shaping the volume of the filters
to get vocal sounds. You may also notice that vocorders have little
effect on consonants. There are ways to use noise in synthesis to get
these sounds and make an audible word. The simplest is just to mix noise
into the waveform before it enters the filter.
The filters used don't mater to some extent. They all should be different
but using a variable state multiple output filter would still work if
you have four vcas. Don't expect too much out of patched together vocal
generators. Using large numbers of bandpass filters, often done with
computer simulation, will make the words clearer and more human, but
it can loose it's transparencty. It seems more engaging to a musical
audience if they can't quite make out the words causing them to guess
and discuss the meaning of something strange when they misunderstood
a mundane lyric.
Getting the sounds you want out of an analog synth take as much practice
as playing the keyboard unless you have a real understanding of it. It
may be hard to imagine an original synthesizer sound when professionals
with omnipotent studios at their disposal can't stop copying 80s club
music and using normal filter effects but keep reading and you may feel
a glimmer of hope!
Mimicking acoustic instruments is not the goal of analog synthesis but
understanding how they work is a real key to generating the sounds you
want. A harmonic, which is also called an overtone, is supposedly an
integer multiple of the main frequency of a sound. There may be harmonics
going on into infinity in frequency but most won't hear them above 20
thousand hertz, nor pure tones below 20 hertz. Some harmonics can be
a little sharp or flat and still be considered harmonic rather than
inharmonic. Partials include these harmonics in most texts and also
any other frequency that makes up a tone. With a waveform or a musical
instrument there is still a fundamental, a frequency which is dominant
and usually the lowest. When you use a waveform other than a sine wave
it is considered to have harmonics even though it appears to be a single
frequency, which makes harmonics and partials hard to understand. It
is interesting to note that by adding sine waves together which can
be generated and mixed normally acoustic sounding signals have resulted.
Even electric organs use partials, for example C at 126 HZ and G at
190 HZ at once will get a difference tone between them of 190-126=64
cycles per second which is C in a different octave. This is why fifths
sound the way they do. Getting a sawtooth wave through additive synthesis
only requires about 14 sine wave harmonics added together. Once added
together they should no longer be visible on an oscilloscope if they
are in their proper position or phase.
Different sounding tones often have the same harmonics at different
volumes. You can alter them with a filter or equalizers. Harmonics can
be measured in decibels and HZ as is sometimes displayed on a digital
equalizer, and remember that equalizers and filters can effect any frequency,
even the fundamental. You can hear just harmonics if you eliminate the
fundamental. In strictly electronic terms altering harmonics like this
does not change any frequencies but warps the waveform with the same
result, so harmonics may be considered abstract to some degree but they
are still quite real. Using the filters resonance will show you on an
oscilloscope that a "ringing" can occur purely through emphasis
on a harmonic area. See the filter and phaser page for more.
Imagine a bugle that has no stops and no keys, how are different notes
produced? Understanding harmonics gives you the answer to some degree.
If you know how to get a harmonic by touching the node of a stringed
instrument like a guitar or bass you can see that different harmonics
are like different notes.
Quoting Bob Moog "There is no such thing as a piano spectrum because
the amplitudes of various piano tone harmonics are constantly changing
with respect to one another in complex ways." He goes on to describe
how the piano's harmonics gradually go sharp as the note goes on while
the fundamental remains the same. Acoustician Harvey Fletcher made an
additive synthesis piano sound with a hundred oscillators that was similar
to the acoustic sound.
Combining 2 waveforms can show you a bit about harmonics. An electronic
organ's bars are pretty much adjusting the volume of those harmonics
and a ring modulator creates unusual partials to make a harsh or pitchless
Combining 2 Signals
Here are some ways to make 2 signals into one with aspects of both.
Mixing 2 sounds together is the obvious way, you can mix several octaves
of sine waves to simulate the harmonics of other waveforms or mix tones
that or not quite at the same note to get a chorus like beating effect.
Mixing two sounds and then applying extremely heavy distortion, or even
some type of sharp clipping, can produce some rarely heard effects often
similar to ring modulation. Of course this effect occurs without distortion
but it is very smooth, and of course you can also hear it with an acoustic
instrument. Distorting a sound can make it more like a waveform. Ring
modulation is an amplitude modulation effect that modulates positive
and negative resting at 0 output when one of it's inputs is quiet. The
vocorder effect makes one signal mimic the treble and bass character
of the other. Oscillator sync can only function with 2 oscillators.
If you chose instead to use a distorted guitar signal, distorted being
more like a square wave, as the soft sync master you would get a weird
effect when you played a chord or solo. You would also get some funny
sounds if you used square wave chords as the sync master. The master
is the sound that determines the overall pitch. There are also various
forms of amplitude modulation, frequency modulation and filter modulation
as well as pulse width modulation for square waves that combine aspects
of the modulator with the main signal. With analog synthesizers you
can use any sound source as a modulator provided it is loud enough.
If you spoke into a microphone and fed that signal only to the fm input
of a VCO you could probably get that VCO to make words.
Just mixing different oscillators with different settings can get the
most unusual sounds and they often sound like it is just one note. When
the first digital synths used waveforms to imitate a piano they tried
tricks like having one oscillator make a click like a key and hammer
mechanism and two or preferably 3 oscillators making string sounds to
mimic each string in one piano note. You don't have to mimic something
to use this method however.
Drones make a really unusual style of music. It imitates instruments
like bagpipes, harmoniums, and snake charmer's pipes but it doesn't
have to be acoustic. A drone is a constant note played underneath a
melody. A drone can be continuous or it can go quiet when the melody
goes quiet, and the best method is combining the two. You usually do
this with a sequencer. Modulating a drone's pulse width or cutoff with
an lfo is good but try some other methods like modulating it slightly
with the melody notes or the cutoff with the melody's keyboard tracking.
Keyboard tracking makes for more variety.
Most synthesizers have a resonant filter. Even if your synthesizer is
a new digital powerhouse of samples rather than an analog one it still
should have a conventional filter like those that made the first synthesizers
so versatile. What you may not realize is that most of the time you
are using it and it may be adding a certain frequency to the sound if
the resonance and cutoff frequency are set right. Sometimes there is
a keyboard tracking adjustment that can shape the way the filter frequency
behaves depending on the note the synthesizer plays. The note and the
filter cutoff frequency can be kept the same at all times if you like
but always try all the different was of setting it.
The cutoff does make a more even sound with the keyboard tracking but
tone is all about getting a more varied sound out of a normal set of
notes, so setting the tracking in an unusual way or turning it off can
help mimic musical instruments or enhance a bizarre waveform. It's also
really good to use other things besides just cutoff. Keyboard tracking
pulse width or ring modulator pitch really makes a difference. If you
play a normal note ring modulated with a note less than a semitone off
it makes a unique sound, so set the modulator pitch's keyboard tracking
up so it's just a little off.
Bad Sounds Good?!
A sideband is a partial, a sine like frequency that is a component of
a sound, which is not in tune with the normal harmonic spectrum. Just
mixing two notes together can produce a sideband electrically or acoustically.
In some cases you can tell what these frequencies will be mathematically.
Amplitude modulation creates sum and difference frequencies. Adding
the number of HZ together and subtracting the lesser from the greater
should give you a good approximation. Filter modulation, especially
with resonance, causes more complicated sideboards and frequency modulation
as well as pulse width seem to cause the most. When these sidebands
are made louder by heavier modulation the fundamental of the original
waveform is overpowered. If the modulating signal is out of the audible
spectrum you may still hear a few sidebands.
When you use vibrato it seems like it just changes the pitch but it
also creates these sidebands thereby effecting the musical nature of
the sound more than you may realize. If you look at a graph of it you
will see it actually warps the waveform more the closer the vibrato
speed is in relation to the pitch of that waveform. If you take a waveform
and feed it into it's own frequency modulation input on an analog modular
synth you simply get different harmonic content and a different waveform.
The most nonsensical sounds can become sweet melody if used right. A
bell can easily have more powerful inharmonic sidebands than it's fundamental
and harmonics. This can make it more effective at alerting people of
something because it's easier to hear above other noises. This is not
the kind of bell that you normally use for music because of it's inharmonious
sound although this is a matter of opinion. If you like modulated or
toneless sounds but want more emotion and melody to them try finding
ways of sequencing and looping them, use the same types of patterns
you use for melody or bass lines. Try an experiment with a ring modulator.
First make it sound really weird and then play a repeating bass line
with it. The tune has no recognizable notes but you may notice a melody
too. Alternating from noisy to melodious makes a good balance and so
does combining them together. Try playing a normal repeating melody
and have a heavily modulated bass line. Then make the melody heavily
modulated and the bass line normal and musical. Noise solos and modulated
arpeggios are fun even if they don't fit into melody things too well.
Getting strange effects
If you have a multi effects processor foot pedal or rack module you
can have a lot of fun with it with a synthesizer even if it is made
for guitar. Often the drawback is that the frequencies are tailored
in a way that eliminates some bass or boosts middle harmonics etc. but
just try it and you shouldn't cause any damage. Digital effects may
not be your thing but often the analog distortion and compression can
make some interesting variations. Never underestimate distortion, it
got all that fame for guitars but it works on any signal.
Analog drumkit sounds
Back when you were combining 2 signals you may have thought about getting
drum sounds. This is best done with a specialized drum module but don't
let that stop you. A normal sounding drum can be made by using an envelope
to control the pitch of a triangle wave an bending it down 2 or more
octaves. It will loose it's quality of pitch and become percussive,
and you can change the filter and pitch to get toms or a bass drum.
If you bend it up from a low note it will be an open tom or hand drum.
When you have a sound you like you can enhance it with another oscillator
that has a shorter duration to make the drumstick on the shell sound.
This tone should also bend down but even quicker than the first. The
snare can be done with this method by adding a third enveloped white
noise sound. If you don't like the result try frequency or ring modulation
on the triangle wave that does the bend. Modulating it with noise will
make a splat sound but if done right it will sound like a weird snare.
Noise used as a modulation source can make a good high hat tone sometimes.