When Tom Oberheim re-entered the synth market in 2009 by reissuing his classic SEM, he adhered to the original design and sound quality as much as modern parts procurement would allow, while adding contemporary features (MIDI-to-CV converter, note-priority modes, a noise source) that expanded the module’s usefulness without jeopardizing the timbre that made it so popular.
I was able to review the new SEM against my own pair of vintage modules, and to match the sound of the originals to a very high degree (keeping in mind that any two analog synths that are 40 years old will to differ from each other slightly). Priced between $899 and $1,199 (depending on the feature set), these new SEMs proved to be a smarter buy for musicians who craved authentic Oberheim sound and wanted an instrument they could use, rather than pay collector prices for a museum piece.
Of course, Oberheim fans immediately began requesting a return of the classic SEM-based keyboards—the Two Voice, Four Voice, and Eight Voice. The Two Voice Pro (TVS-Pro), as it is now called, is first in a proposed line of these instruments. And like the SEM, it is more than a simple ’70s redux: Oberheim added a range of features that were unavailable on the original, but that modern players expect, while maintaining the vibe of an earlier era.
As its full name implies, the Synthesizer Expander Module of 1974 was originally designed to be an accompanying voice for monosynth users. Featuring two VCOs (each with sawtooth and pulse wave choices), an LFO, a resonant 2-pole multimode filter, and two 3-stage envelope generators, the SEM could be used to fatten up the sound of your main keyboard or be driven by the Oberheim DS-2 digital sequencer, so you could use your monosynth for bass or lead duties. The SEM’s 2-pole filter response also gave the module a distinctive timbre at a time when the Moog and ARP 4-pole sound was prevalent.
A year later, Oberheim grouped SEMs together with a polyphonic scanning keyboard to create the Two Voice and Four Voice, the first analog polysynths with independent voltage-controlled voices. These stacked SEMs were capable of creating massive tones that drew the attention of major artists.
But the strength of the system also proved to be its biggest drawback: Like all analog synths of the time, each SEM voice had to be individually tuned and programmed—a time consuming affair. A programming module was eventually introduced for the 4-and 8-voice systems, allowing you to save and recall some module parameters. Then Sequential Circuits introduced the Prophet-5, which could control and store analog parameters using microprocessors, forcing Oberheim and other manufacturers to follow suit with their subsequent instruments.
However, Tom recently told me that the SEMbased instruments remain his personal favorites from the Oberheim line, for the very reason that each voice was a fully independent synthesizer “with a life of its own.” As far as he’s concerned, that’s the basis for their rich tone and musicality.
Consequently, at the core of the TVS-Pro is a pair of independent SEMs—one for each voice. And like the reissued modules, the SEM voices enhance the mid-’70s design, in this case with the addition of two VCAs (one to provide velocity control over the amount of Envelope 1 modulation of the other VCA and another for Envelope 2 modulation of the filter). Again, these provide extended functionality without altering the basic sound of the SEM.
The TVS-Pro’s raison d’être, however, is the implementation of the modules into a keyboard-based performance system, with the ability to set up and store keyboard, controller, and sequencing functions. So, parameters such as MIDI channel, pitchbend range, velocity curve level, keyboard mode, and split points are retained when you cycle the power. But as with the original Two Voice, there are no patch save/recall capabilities for synth voices—by design; Oberheim invites you to explore the sonic capabilities.
A surprising and welcome improvement of the TVS-Pro over the original Two Voice is a significant reduction in size and weight. Gone is the heavy wooden road case of the ’70s, in favor of a metal chassis with wooden endcaps that feels solid, overall.
The 3-octave keyboard’s action is robust and smooth under the fingers and offers velocity and aftertouch control over the analog sound as well as MIDI. The Bendbox, to the left of the keyboard, provides pitchbend and modulation wheels, a 1/4" headphone jack (with volume control), and an independent vibrato LFO (patched to both voices) with knobs for frequency and depth/assignment. (The latter determines whether you introduce vibrato using the mod wheel or key pressure/aftertouch.) There is also a section here for transposing each voice up or down two octaves when using the keyboard for control.
The Bendbox also includes a Fine Tune control to alter the pitch of all four oscillators (e.g., both voices) and the VCO2 Detune knob that subtly changes the pitch of VCO 2 on both modules, to beef up the sound. Because the Fine Tune knob is just above the mod wheel, care must be taken so that you don’t accidently hit it. (Speaking of tuning, the TVS-Pro provides a 440Hz tone for calibrating the oscillators.)
Along with Unison and Split keyboard settings, the TVS-Pro provides several keyboard-control modes. You can select whether or not a new note triggers envelopes, alternate between SEM A and B with each new key press (Polyphonic Two Voice Toggling, or Rotate mode), or use SEM A First mode, which only triggers SEM B when a second key is held down. You can further customize the instrument by selecting one of the 8 velocity curves for the keyboard as well as setting the range of the pitchbend wheel (from 1 to 12 half steps). Unfortunately, upper-or lower-note priority modes are not available.
The TVS-Pro’s Mini-Sequencer lets you program up to 16 steps for each voice, with the ability to introduce rhythmic variety by adding 2-, 3-, and 4-gates per step (called Ratcheting). I immediately programmed some sequences with contrasting ratchet rhythms in each voice, and then used the onboard mixer to hard-pan the voices to the TVSPro’s stereo outputs.
Moreover, as a sequence plays, you can easily alter the number of steps or jump to a new sequence (when the previous sequence ends) without stopping. The programmer stores 50 sequences, and chains of sequences can be assembled into songs and saved into one of 9 memory slots. As you assemble a song, the individual sequences can be repeated and transposed as desired.
On the review unit, the sequencer notes could only be selected using the pitch knobs above each step. An upcoming firmware update (available this month) will add keyboard note-input, which will make sequencing a lot quicker and more intuitive.
Outside the Box
The ability for the TVS-Pro to play each SEM individually from the sequencer, or triggered from the keyboard or sample-and-hold generator. suggests a number of performance options: You could use the sequencer to control SEM A while you play a bass or lead with the other module: Then select KeybTrans to transpose the sequence in real time by playing notes on the keyboard. Another option is to assign a split point anywhere on the keyboard and play SEM A with the left hand and SEM B with the right.
Because the TVS-Pro is semi-modular, you can further extend its sonic potential by utilizing the 56 mini-jack patch-points on the top panel. With these, you can introduce modulation paths between the two SEM modules, expand the control of the sequencer and keyboard over the voices, and integrate external synths (such as a Eurorack system) into any of the performance scenarios above. Each VCO (two per SEM voice) has independent outputs for sawtooth and pulse waveforms, an LFO, a pair of envelopes, and for the bandpass and highpass/lowpass filter. There are also voltage-control inputs for each VCO, as well as the filters, envelopes, LFOs and VCAs.
You can also take CV outputs from the mod wheel, vibrato LFO (controlled by mod wheel or aftertouch), velocity A and B, aftertouch, and the sample-and-hold circuit, as well as CV and gate signals from each sequencer track. The rear panel provides 1/4" audio inputs (to process external sounds through the filters) and CV and gate outputs for each SEM voice, in addition to standard MIDI In, Out, and Thru connectors.
The TVS-Pro handles basic MIDI messages from the keyboard and sequencer on one or two channels, depending on your playing/sequencing requirements, and the sequencer can sync to MIDI Clock. As a result of user feedback, new features are being added through firmware updates. In addition to the aforementioned ability to program the sequencer from the keyboard, the next firmware update will allow you to put the machine in Local Mode, so you can use the TVS-Pro’s keyboard to play 8 voices on a polyphonic synth over MIDI while using the Mini Sequencer to control the internal SEMs—yes!
The Next Vintage
Whether you’re talking price or design, the TVS-Pro is not a cheap instrument. Sure, $3,495 seems high for a 2-voice analog synth and sequencer in an era when major manufacturers are pricing their own analog synths well below a grand. Yet despite the name recognition, Tom Oberheim is not a major manufacturer, nor is he working at that scale. You’re paying for a fully professional instrument, built and tested in California, that offers the classic Oberheim sound. This is the real deal, not an approximation or clone.
If you take into account what you’re getting for the price—two MIDI-capable SEMs with patch points ($1,199 each); a high-quality 3-octave keyboard (with velocity and aftertouch); the Bendbox features; programmable controls; the Mini Sequencer; MIDI connectivity; and a case with power supply and internal connections—you will see the value.
For me, the main draw of the TVS-Pro is first and foremost its sound: Two SEM modules that provide the palette of desirable Oberheim timbres—thick bass tones, complex and buzzy leads, and chirpy percussion just for starters. Then there is the user interface—a classic combination of a 3-octave keyboard and dedicated controls for every parameter, to mold sounds in an organic and intuitive way while playing. Just as significant, the patch panel and MIDI I/O let you integrate the TVS-Pro into any studio and stage setup and is particularly inviting for modular users.
In short, the TVS-Pro is a long-term investment in a quality instrument that will long outlive every Oberheim software emulation you’ll ever own, as well as the computers they run on.
PROS Two SEM modules. 2-track, 16-step sequencer. Several keyboard performance modes. Smooth keyboard action with velocity and aftertouch. Mini-jack patch points. MIDI I/O.
CONS Pricey. Fine Tune knob too close to Mod wheel. No traditional note-priority settings.
The sound of an Oberheim Two Voice at a reasonable price and with features unavailable in vintage models.