The Sequential Circuits Prophet-5, which debuted in 1978, was the world's first fully programmable polyphonic synthesizer. Although the Prophet-5's total sales figures never approached those of the popular synths of the 1980s, it has a mythic status due to both its warm analog sound and its unique position in history. The elegant wooden end panels add a coolness factor as well. Unfortunately, real Prophet-5s are hard to find and even harder to keep in good repair.
FIG. 1: In Hybrid mode, Arturia Prophet-V combines the features of a Prophet-5 (bottom) and a Prophet-VS (top). The joystick (upper left) can be assigned to two MIDI Control Change messages, so you can sweep through the oscillator mix in real time.
Given Arturia's quest to model the most popular vintage analog synths, it is not surprising that the company has created Prophet-V 1.0. However, Arturia went one step beyond merely mimicking a Prophet-5 by including a clone of the Prophet-VS, an instrument that used vector envelopes to crossfade between four oscillators playing single-cycle digital waveforms. To top it all off, Prophet-V offers a Hybrid mode, which lets you create patches that combine the voicing features of both instruments (see Fig. 1). All three modes share certain features, including 32-note polyphony, external MIDI control of most parameters, and two effects processors (a chorus and a stereo delay).
Prophet-V can operate as a standalone instrument or as a VST, AU, DXi, or RTAS plug-in. I used it in standalone mode and as a VSTi on my main Windows computer, a 3 GHz Pentium 4. A Syncrosoft USB dongle is used for copy protection. I compared the appropriate sound and features of Prophet-V with those of a real Prophet-5 owned by Rick Eberly, a former Sequential Circuits employee who currently provides repair services through Wine Country Productions in San Jose, California.
The Prophet-5 emulation in Prophet-V offers what you would expect: two oscillators (A and B), a resonant 24-dB-per-octave lowpass filter, two 4-stage (ADSR) envelopes, an LFO, a mixer, a VCA, a noise module, and a polyphonic modulation (poly mod) section, which helped define the sound of the original instrument (see the sidebar “The Real Thing”). Rather than simply replicating the Prophet-5, Prophet-V adds a number of welcome enhancements, such as antialiasing oscillators, an effects processor, and a monophonic Legato mode.
Arturia has been careful to keep the look and feel of the original Prophet-5 while doing its best to reproduce the synth's signature sound. For example, Prophet-V's filters sound rich and organic when being modulated by Oscillator B. I spent some time duplicating a modulated filter patch created on the Prophet-5, and the Arturia version was able to nail the sound.
At first glance, Prophet-V is almost too faithful to the original. There's no Velocity response, for instance, unless you switch to Hybrid mode and use the Velocity modulation routings on the VS side. The original set of 40 factory patches is included, and they are accessed in 5 banks using a set of 8 buttons, as on the original. (The remainder of the 400 patches included in Prophet-V are accessed from a pull-down menu rather than through the panel buttons.)
Next to the Unison button is a knob that controls the amount of detuning, which is useful because a digital instrument doesn't exhibit the random pitch fluctuations from voice to voice that an analog instrument does. This knob is active even when Unison mode isn't. Turning it up causes the exact intonation of a given interval to change due to voice reallocation, just as it did on the Prophet-5.
Prophet-V has an “analog tone” modulation source that causes rapid, subtle fluctuations in waveform pitch and phase. The depth of this modulation ought to be user programmable, but it isn't. In the low register, the tone of Prophet-V sounds significantly less stable than that of the Prophet-5 I compared it with. I didn't care for the sound quality of this tone; it made me nervous. Possibly the instrument Arturia used as the basis for its model wasn't in good condition.
Prophet-V's LFO has a Sync button, which locks its rate to an external MIDI clock. In sync mode the LFO has only 16 possible rates: from 8 beats through 1 beat, and from ½ through 1/9 beat. Certain useful values seen almost universally in syncable LFOs, such as dotted quarter notes and dotted eighths, are not available — a glaring oversight.
Every control on the Prophet-V panel can be linked to an external MIDI Control Change message. When I attached a MIDI slider to the filter cutoff knob using the Learn function, I was pleased to hear how smoothly the filter responded — my slider sounded like a component on a real analog synth. Another nice touch is that the position of the onscreen mod wheel is stored with the preset. This allows sounds to have built-in vibrato, which was not possible on the Prophet-5.
A Vector in the Mix
The Prophet-VS introduced the concept of two-dimensional vector envelopes, which after the demise of Sequential Circuits were adopted in the Yamaha SY22 and Korg Wavestation. The VS had four oscillators that played single-cycle digital waveforms, and the vector envelope was used for crossfading among the oscillators.
While the voice architecture of Arturia's Prophet-VS is much the same as that of the original, this side of the software is considerably less authentic than the Prophet-5 side. The front panel is quite different. The VS's arpeggiator (described by Julian Colbeck in Keyfax Omnibus Edition as “the bee's knees”) is missing, and the filter response is multimode rather than strictly lowpass. There is no facility for loading your own waveforms into slots 0 through 31 of the wavetable; only the 96 factory waves are available.
I couldn't locate a Prophet-VS for comparison, but I vividly remember that its digital wavetables aliased quite markedly in the upper register. Fortunately, Arturia has eliminated this rather horrible sound.
The Prophet-VS has two LFOs, three envelopes (two are 5-stage envelopes, and one is a 4-point envelope for the VS Mixer), and an unusual panning mode that allows individual voice channels to be given static panning positions for a big stereo spread. The Arturia VS can produce some sweet “vintage digital” sounds, especially when envelope looping is applied.
Common to both the Prophet-5 replica and the VS replica is a choice of High, Low, Last Note, Reset, and Circular voice assignment modes. The first three produce monophonic results. In Reset mode the lowest-numbered available voice is used, while in Circular mode the synth cycles through its available voices. If your patch has a long envelope release, Reset mode will steal notes that may still be sounding if the key has been lifted, which may not be what you want. Unfortunately, Circular mode produces nasty crackling distortion, so it won't be usable until Arturia fixes the bug.
The modulation matrix allows 8 sources to be patched to 15 destinations, but with some limitations. For instance, the keyboard can control oscillator mix, filter cutoff, or panning, but not LFO rates and amounts. Each source has only one amount parameter, which is applied to any destinations that are switched on for that source. This system is a bit primitive but usable. The maximum depth available for any modulation source is 1.00. The units are arbitrary, and may be different for different sources, but in general I felt that more modulation depth should have been allowed. The maximum amount of Velocity to amplitude, for instance, just isn't dynamic enough to suit me.
FIG. 2: In Hybrid mode, Prophet-V''s four oscillators (left) can mix Prophet-5 analog models with Prophet-VS digital wavetables. Active signal connections are shown in orange; here, the two filters are in series.
In Hybrid mode, the features of the Prophet-5 and the VS are integrated. Four oscillators in all are available; the first two can be from either the Prophet-5 or the VS. Oscillator mixing is handled by the VS joystick and vector envelope. The two filters can operate in parallel or in series. What's unusual about the series routing (see Fig. 2) is that both VCAs are still active. This lets you use the two amplitude envelopes to crossfade between the sound of the VS filter by itself and the series output.
By using Hybrid mode but ignoring the VS oscillators, you can create Prophet-type patches with extra LFOs, envelopes, and so on. I like having this kind of flexibility.
What Shall It Prophet?
Overall, Arturia Prophet-V replicates the sound and feel of the Prophet-5 very well, while adding a number of features that modern synth users will want. With the inclusion of the VS model and Hybrid mode, Prophet-V offers plenty of bang for your buck.
Jim Aikin is a regular contributor to EM and other music-technology magazines, a cellist, and an author. You can visit him online atwww.musicwords.net.
THE REAL THING
Sequential Circuits (the name was later changed to Sequential) built a line of Prophets, including the original Prophet-5, the Prophet-10, the Prophet-T8, the Prophet-600, the Prophet-VS, the Prophet-2000, and the Pro-One monophonic synth. None of the later models achieved the popularity or legendary status of the Prophet-5.
The Prophet-5 was capable of 5-note polyphony and had a bank of 40 memory locations for storing presets. (Offline storage was handled using an analog-tape cassette interface.) The actual synthesizer was analog throughout, but digital circuits were used both to scan the keyboard and to store the settings of the knobs and buttons. There was only one audio output.
The Prophet-5 voice had two oscillators and a noise source, a resonant lowpass filter, a low-frequency oscillator, and two ADSR envelope generators. The release segments of the latter could be switched on or off with a Release button, a feature borrowed from the Minimoog. A Unison button created a big monophonic sound by assigning all five voices to a single key. Because the oscillators were analog, there were always small discrepancies among them in pitch, so Unison mode provided a fat, chorused sound.
Oscillator A had two waveform choices, a square wave and a sawtooth. Both could be active at once. A Pulse Width knob controlled the square wave's shape, and a Sync button could be used to sync the frequency of Oscillator A to Oscillator B. Both A and B had frequency knobs for tuning in half steps.
Oscillator B had three waveform buttons (sawtooth, square, and triangle), selectable in any combination. A fine-tuning knob allowed Oscillator B to be detuned from A. Next to Oscillator B's Pulse Width knob were two more buttons. One switched Oscillator B into low-frequency mode, allowing it to be used as a second LFO. The other enabled or disabled keyboard tracking. When tracking was switched off, Oscillator B produced a tone at a constant frequency.
The LFO and noise source could be used for modulation in the Mod Wheel section, which had five destination buttons (the frequencies and pulse widths of the two oscillators, and the filter cutoff). A Source Mix knob in this section allowed the LFO signal to be crossfaded with the noise source. The depth of modulation was set directly from the mod wheel. Aside from the mod wheel, there was no way to add vibrato.
The Poly Mod section had two Source Amount knobs, one for the filter envelope and one for Oscillator B. Three destination buttons were provided, for the frequency and pulse width of Oscillator A and the filter cutoff. The Poly Mod section was responsible for some of the Prophet's most evocative sounds. It could be used to control Oscillator A's pitch or pulse width from the filter envelope, and also to drive the filter with an audio-rate signal from Oscillator B.
The Prophet's other features included a glide-rate knob, a button that produced a reliable A-440 for tuning purposes, and a handy tune button that caused the instrument to tune itself. Tuning required several seconds, during which the Prophet produced no sound. Typically, tuning was required several times while the instrument warmed up and about once an hour afterward.
software synthesizer $249
FEATURES4EASE OF USE4QUALITY OF SOUNDS4VALUE4
RATING PRODUCTS FROM 1 TO 5
PROS: Authentic sound. Hybrid mode adds many features. Smooth response to MIDI Control Change messages.
CONS: Prophet-VS design is not fully authentic.