By Jim Aikin
WANT GOOD VIBES? CHROMAPHONE HAS THEM—ALSO GOOD MARIMBAS,
xylophones, bongo drums, chimes, gongs, plucked strings, and more. This plug-in
synth uses physical modeling to produce a wide variety of struck and plucked instrument
sounds. Some are amazingly realistic, others so exotic they could come from another
planet. The tone is detailed and musical, but I wouldn’t call it fat. No samples are
employed—all of the sounds are synthesized in real time. This adds expressive power,
especially in the velocity response, but a fast computer is highly recommended.
Chromaphone is not an especially deep or complex
instrument. It’s not packed with hidden options:
A glance at the front panel says it all. The
synthesis engine is not your standard oscillator/
filter layout, however. When you start designing
your own sounds, you’ll find that the controls
interact with one another in unusual ways.
There’s more sonic power here than meets the
eye, and a bit of trial and error may be needed to
get the sound you’re searching for.
At the root of Chromaphone’s modeling
are resonators (things that vibrate) and exciters
(things that strike or pluck the things that
vibrate). On the left side of the panel are two
sources for excitation signals: a mallet and a noise generator. The signal from these is sent to
a pair of resonators. Depending on what resonators
are used and how they’re programmed, a
simple excitation signal can produce a huge variety
of tones. Eight different resonator types—
string, beam, marimba, membrane, plate, closed
tube, open tube, and manual—are provided.
Rounding out the feature set are a vibrato
LFO, a general-purpose LFO, and a pair of effects
processors. The 20 effect types include all the
things you’d expect, from chorus and reverb to
tremolo, EQ, and overdrive.
Modulation depth is displayed in pale colored
arcs around the knobs, and also numerically
when the depth is being edited with the mouse.
The pale arcs are a bit fiddly and hard to see, but overall the user interface is very sensibly
designed: Inactive controls are grayed out, modulation
depth can be zeroed by double-clicking, a
preset browser is tucked away under the Manage
button, and so on.
The mallet source produces a brief impulse at the
start of each note. It has four knobs: Volume, Stiffness, Noise amount, and noise Color. The first three
can be modulated by key number and/or velocity. When the stiffness is low and the noise amount is
high, a softly brushed attack is produced. When the
stiffness is high you get a snappy attack.
In addition to the noise in the mallet source,
Chromaphone has a second, more flexible noise
source. Its main purpose is to give you an ongoing
signal that can generate sustaining sounds. It
has Volume, Frequency, Q (width), and Density
knobs. The Frequency and Q knobs control a
multimode filter that processes the noise signal,
and this filter has its own five-stage envelope,
with a delay segment upstream of the expected
attack, decay, sustain, and release.
A low setting for noise density can produce
a pleasantly randomized repeating attack, reminiscent
of wind chimes. I spotted a minor bug
in the version 1.00 release, however, that causes
extremely low settings for this knob to shut off
the output of the noise source. I’m told this bug
is only in the Windows version. The volume, filter frequency, and density of the noise can be
modulated by key number, velocity, or the LFO,
and both frequency and density can be modulated
by the envelope.
Using the Direct slider, you can mix the signal
from the sources straight into the output,
bypassing the resonators. This is useful for hard
attack clicks, wind noise, and probably a few
The resonators are the heart of Chromaphone.
They can operate in parallel, providing two independent
resonances from the same excitation
signal, or they can be coupled. When they’re
coupled, the output of resonator A feeds the
input of resonator B, but there’s also a feedback
loop, causing B to add energy back to A. This
emulates the behavior of physical instruments.
In an acoustic guitar, for instance, the energy of the vibrating string flows into the soundboard,
but the vibration of the soundboard also affects
the vibration of the string.
The balance/coupling slider at the far right of
the screen controls the volume balance between
the two resonators when they’re not coupled,
and their relative stiffness when they are coupled.
The position of this slider can be modulated
positively or negatively by MIDI note number. It
has a surprisingly large effect on the tone.
With a couple of exceptions, the resonators
each have five knobs: Decay, Release, Material,
Tone, and Hit Point. They also have inputs for
LFO modulation and a built-in pitch envelope
with amount, decay time, and velocity response
sliders. The exceptions are the closed tube and
open tube, which only have knobs for Decay,
Release, and Radius (i.e., how big around the
tube is) and don’t allow LFO or pitch envelope
Also omitted from the tube models is a fourposition
complexity switch. With this switch you
can control the number of partials that will be
generated by the resonator. More partials will
give a more complex and realistic tone, but at the
cost of some extra CPU usage.
Pitch modulation in Chromaphone can occasionally
cause undesirable behavior. With either
LFO modulation or a pitch envelope, a resonator
can go into runaway digital overload, resulting in
a really loud and nasty sound. This doesn’t happen
often, but it happened more than once while
I was working on this review.
The Material knob models the difference between
rigid and loose materials by adjusting the decay and
release times of the higher partials in relation to
the lower ones. When the material is stiff , the high
overtones last longer; when it’s less stiff , the high
overtones die out faster than the lower ones. The
tone knob does something similar, balancing the basic
amplitudes of higher and lower overtones rather
than off setting their decay times.
The Hit Point knob adjusts the physical
location in the model at which the excitation
signal interacts with it. With a string model,
for instance, this knob gives a realistic impression that the string has been plucked nearer the
bridge or nearer the middle. The tube models
don’t have a hit point, because a signal can
enter a tube only at its end—think of a flute
or pipe organ. Decay time can be modulated by
MIDI key number, and hit point by key number,
velocity, or a random source.
The two resonators can be tuned independently,
and the pitch of each of them can track the
keyboard fractionally. Some of the most interesting
percussion sounds in Chromaphone are
achieved by detuning and fractionally scaling
one or both resonators. With the manual resonator,
you have independent pitch control
of four sine-wave partials—and they aren’t
restricted to whole-number multiples of the
fundamental pitch, so bell tones and other
things with interesting harmonics are easy
The tricky aspect of fractional keyboard pitch
tracking is that when the resonators are coupled,
they will be much more in tune with one another
on some keys than on others. This can cause
certain notes or keyboard zones to sound much
louder and with more sustain than other notes or
zones. This isn’t a defect; it’s the nature of physical
Chromaphone can’t load alternate tuning
tables. For an instrument that does a fine job
with metallophone timbres such as you might
hear in a gamelan, this is a significant omission.
Incredible as it may seem, Chromaphone
does not respond to MIDI pitch-bend. Given the
possible instability of a physical model when the
pitch is being modulated in real time, and given
the fact that you can’t pitch-bend a marimba or
a gong while it’s sounding, I’m almost (but not
quite) willing to give Applied Acoustics a pass
on the absence of pitch-bending. The pitches of
the resonators can be automated in your host
sequencer, so you can draw bends or “play” them
in with a controller if you need to.
More than 300 presets are included with
Chromaphone, in a dozen categories. Not
surprisingly, they’re strongest in the mallets
and chimes departments. One of the categories is called “Kits,” but this is something of
a misnomer as Chromaphone lacks the multitimbral
keyboard mapping that’s normally
required for a drum kit. The Applied Acoustics
website says that Chromaphone comes
with “ready-made creative kit patches where
each note provides a new sound slightly different
from the previous one. Over the entire
keyboard range the sound morphs from bass
drum to snare to hi-hat.” The sound does indeed
morph—mainly due to keyboard scaling
of the Pitch and Hit Point parameters. The
end result, though, is glitchy sounds that,
while they might play the roles of kick, snare,
and hi-hat in a rhythm track, sound neither
like real drums nor old drum machines. Listen
to the “Chrompahone Kits” audio clip I posted
online and judge for yourself.
The electric pianos don’t sparkle as much
as I’d like, but the Clavinet has a nice bite. The
bongos, clay drum, and high tabla are crisp and
useful. The “Woody E. Bass” and “Velo-Slap
Bass” are satisfyingly full-bodied, but I felt some
of the other basses were trying a little too hard.
The patches in the “Strings & Pads” category
are breathy or raspy, because they use the noise
source to create a sustaining tone.
In the “Plucked Strings” bank, “Electric Contemplation”
has a rich hollow-body electric tone,
“Soft Harp” does the job, and “Inverted Dulcimer”
has the kind of crazed edge you’d expect
from a prepared piano. Chromaphone does a nice
job with organ pipes, thanks to the tube resonators
and the noise source.
Chromaphone delivers a surprising variety of
expressive sounds, and gives musicians some
unusual and useful kinds of control. I’m not a big
fan of velocity cross-switched multisamples
(and Chromaphone doesn’t use them), so I’m
especially pleased with how smoothly and
naturally Chromaphone responds to velocity.
Programming your own sounds in a physical
modeling synth can be a bit intimidating at first,
but coming up with evocative new sounds turned out
to be far easier than I expected. Chromaphone
is a specialty item, not a do-everything workhorse
synth, but it’s sure to find a home in
PROS Great for chimes, mallets,
and pipes. Expressive
velocity response. Detailed
tone colors with unusual types
CONS Doesn’t receive MIDI
pitch-bend. No alternate
Realistic physical models of struck
and plucked instruments, with lots
of ways to tailor the sound.
$199 list | $185 street
FORMATS VST or AU plug-in.
SYSTEM REQUIREMENTS Mac:
OS X 10.5 or later. PC: Windows
XP SP2 32-bit or Windows Vista
or 7 32- or 64-bit. Both: 512MB
RAM, 70MB free hard drive space,
1024 x 768 display resolution.