VCO Pack

The Prophet X VCO Sample Pack is a community effort to bring classic VCO sounds into the Sequential Prophet X as user samples. Long unfiltered samples were captured for every key across a 73-key range from C0 to C6 to reproduce the natural variation of each instrument. A variety of configurations appropriate to the source were used to reproduce a range of useful raw oscillator sounds.

The pack currently includes four instruments: Behringer Neutron, Sequential OB-6, Dreadbox Erebus, and Moog Voyager. As a bonus, there's also a pair of stereo oscillator stacks combining multiple analog instruments.

02. Triangle
03. Saw
04. Square
05. Dual Saw
06. Dual Saw Alt
07. Dual PWM
08. xMod PWM
09. Saw Trio w M32

These keymaps showcase a modern CEM3340 oscillator IC, manufactured using the same design and specifications that contributed to the core sound of classic instruments including:

  • Cumar Spirit
  • Moog's Memorymoog
  • Oberheim OB-8 and OB-Xa
  • Roland SH-101 and Jupiter-6
  • Sequential Circuits' Pro One, Prophet 5 rev 3, Prophet 10, Prophet T8, and Prophet 600

The final keymap routs a dual sawtooth configuration externally through a Moog Mother-32 to layer yet another sawtooth wave for additional thickness and variety.

10. Triangle
11. Saw
12. Saw PWM
13. Square
14. Pulse
15. Narrow Pulse
16. PWM
17. Saw xMod Square

These keymaps showcase a discrete design manufactured by Sequential in a collaboration between Dave Smith and Tom Oberheim as a callback to classic Oberheim sounds.

20. Triangle
21. Saw
22. Square
23. Pulse
24. Narrow Pulse
25. PWM
26. Fast PWM

The Dreadbox Erebus has a classic character that is closer to pure mathematical waveforms than anything else in this pack, tending toward bright, aggressive tones that are consistent in amplitude across the keyboard. The unit sampled here is a version 2 model.

30. Triangle
31. Saw
32. Square
33. Pulse
34. Narrow Pulse
35. Saw-Square
36. Triangle-Saw
37. Dual Saw Square
38. FM Saw Square

The Saw-Square and Triangle-Saw oscillators are half a cycle of one waveform followed by half a cycle of the other, yielding a unique harmonic character. The FM sample blends a sawtooth wave frequency modulated by another sawtooth, layered with a square wave.

This particular Voyager has the slew rate mod which brings a little more high end content to the raw oscillators of this classic synthesizer. Its character is achieved by taking substantial liberties with the wave shapes. Looking for a very soft muted triangle, a nasal sawtooth, or a bright buzzy square? This is the one.

90. Stereo 7 Saws
91. Stereo 7 PWMs

Four synthesizers were stacked here. It starts with two detuned DCOs from a DSI Evolver hard panned in stereo as a foundation. A Sequential Prophet 6 contributes two VCOs alongside a subtle touch of noise, all centered to anchor the sound. There are two Moog Voyager oscillators as well, offset from center with a subtle touch of filtering to give each side a unique character, accompanied by another hint of noise. Lastly, a Moog Mother-32 adds a seventh oscillator centered in the stereo field.

The same configuration is used twice: once with seven sawtooths and again with seven pulse oscillators that have subtle pulse width animation applied.


Start with a USB storage device formatted by the Prophet X (from the synth's Global menu select 35-Format USB Drive.) Plug the USB drive into your computer, and create a directory named "px" at the root of the drive. This is where anything the synth can "see" will be copied, including firmware updates, so the process may already be familiar.

Copy the entire "u02" directory contained in one of the downloads into the "px" directory (or combine multiple downloads by merging their u02 directories into one.) At this point you should have a directory structure like "/px/u02/15 Synth" that contains a collection of encrypted .zip files. Unlike the original download, these .zip files aren't intended to be decompressed, just leave them as is. The Prophet X understands their format and decrypts them internally.

Plug the USB drive back into the Prophet X. From the Global menu, select the 34-Update Library option, and use soft knob three to switch the installation type to User. Start the installation, which will take a couple of minutes. When complete, try selecting one of the samples by holding the Group button and turning the Type encoder until it shows "User 3", then release the Group button and turn the Type encoder to select category 15. Synth. All the samples you've downloaded and installed should be now be selectable. Enjoy!

(The u02 directory corresponds with the sample group User 3. The directory name can be changed to control which group the installation occurs in, but it must be in the range u00 to u31. These correspond to the groups User 1-32 for reasons only a software engineer could love.)


Thanks to the community for their collective interest in getting this project started. The first step was taken by @blewis_13 in providing his Neutron VCO recordings and following up with the Voyager and stereo analog stacks. OB-6 and Erebus samples were contributed by @AlanC3. Sample editing, looping, packaging and hosting by @Lady Gaia.


The content of this sample pack is provided AS IS with no implied warranty. Install at your own risk, knowing that you accept full responsibility for resolving any issues that may arise.

Audio Sample

The opening drone and pad consists of a Voyager Dual Saw + Square layered on an Erebus Fast PWM oscillator plus a Prophet X supersaw. There's some LFO induced instability during the attack that fades out quickly, and a sample/hold random sine wave drifting around subtly that emerges only in the release. All of this in a single program.

The percussive bass that enters next uses Square and Triangle Neutron samples on their own. Just filter and amplitude envelopes with not much else.

The drums were sampled from a Roland R-8M so everything could be done on the Prophet X. These feature the only reverb in the demo, utilizing the Super Plate for some spaciousness along with a resonant high pass filter to beef up the kick.

The final bass featuring some glissando with different rates on several elements is a combination of the Erebus Square and OB-6 Saw PWM waves along with Prophet X saw and square for some over-the-top thickness. A touch of chorus and the same high-pass filtering trick used on the drums help spice it up further.

Waveform Comparisons

Version History


Added stereo analog stacks as bonus material


Added Erebus content

Added Voyager content


Added OB-6 content

Added Neutron samples for black keys unintentionally omitted from v1.0

Renamed the collection to "VCO Pack"

Revised naming to follow established Prophet X conventions


Initial release of Neutron VCO pack