VIRSYN Poseidon 1.4

This software synthesizer uses analysis/resynthesis (A/R) as its basic sound engine.
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Web Clips: Listen to audio examples of presets, samples, patches, and more from the Poseidon software synthesizer

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Fig. 1: Poseidon's main screen provides access to all the major program controls and displays a list of attributes for finding presets.

Poseidon 1.4 is a new software synthesizer from the always-innovative VirSyn. Unlike many recent soft synths, the program uses analysis/resynthesis (A/R) for its basic sound engine and provides up to 512 sine waves for the reconstruction of the included or your own analyzed sound files. Combining the powerful capabilities of A/R with components from VirSyn''s other offerings, Poseidon adds to the company''s already-impressive sound-design tools.

Riding the Waves

Anyone familiar with VirSyn products will recognize many of Poseidon''s interface elements. At the bottom of the main screen is a 7-octave keyboard for triggering sounds and a panel containing the knobs, wheels, and text fields you use to control program parameters (see Fig. 1). Above that is the Sound Browser display, which shows preset names on the left and several categories of attributes on the right. You use the Sound Browser like a database by specifying the attributes of the sound you are looking for, whereupon Poseidon will locate the presets that match your criteria. The Sound Browser display toggles with the Spectrum window, which offers different modes for viewing the frequency and amplitude components of your sounds and provides access to several other functions (see Fig. 2).

VirSyn''s trademark Slot Machine (Randomize) icon appears at the upper right of the main screen, as do an icon that triggers an All Notes Off message, a button to link to the company''s Web site, and a MIDI icon that toggles the display of the controller mappings for all the main program controls. The mappings can''t be edited from this display, but a very simple MIDI Learn option is available. You can use the Slot Machine to jump-start ideas: let it create new patches by mixing parameters from existing ones. I found the results to be usable a high percentage of the time (your odds may vary).

Under the Surface

Poseidon''s basic architecture includes a spectrum-modeling oscillator, several filters, two LFOs, three ADSR envelope generators, and a small set of effects (up to four can be enabled at once). Though most of these components are standard issue for a modern soft instrument, Poseidon offers some unique capabilities that you won''t find on your average synth.

For example, the new PoleZero filter allows you to custom design two separate filter topologies, each containing eight poles and eight zeros (notches), and then manually or automatically morph between them. Designing the filters is very intuitive, as you can both see and hear changes you make in real time. You can copy the filter structures from one patch to another, but you can''t save them to disk as independent elements.

Another unique filter option is the new Inverse filter. This filter extracts the resonant characteristics of a sound and lets you map them onto another sound. For instance, you could apply the resonant model of a bell sample onto an acoustic instrument sample to give it a bell-like quality (see Web Clip 1).

Even more powerful is the ability to freely substitute spectral-analysis files (which Poseidon calls “models”) between patches. Choose a preset such as Electric Piano, with its short attack and moderate release times, then substitute the analysis of a vocal sample for the model that the EP preset uses by default, and you''ll get a sound that mixes characteristics of the piano with a vocal timbre (see Web Clip 2). Poseidon ships with more than 100 analysis files that you can freely interchange among the presets, and you can also make your own by analyzing any samples you have on hand.

The analysis process is very flexible: you can tweak settings to best fit pitched or nonpitched material, and you can alter the window size used by the analysis (smaller windows give better temporal resolution and larger windows give better frequency accuracy). You can also specify how many partials the resynthesis will employ (from 1 to 512) and whether only harmonic partials will be used or if inharmonic partials will be allowed.

Another powerful feature, found in advanced analysis/resynthesis software such as SMS (see the home page of Xavier Serra, a key researcher in this technique, at for more information), is the ability to isolate the pitched component of a sound from its noise component (called the residual). You can change the mix amount of the pitched and nonpitched elements, which allows you to, for example, hear only the airy portion of a flute sample or the noisy fricatives of a vocal sample (see Web Clip 3).

Totally Submerged

Poseidon provides other high-end analysis/resynthesis features that give you even more sound-design potential. For instance, because you have access to the individual components that make up a sound''s spectrum, you can alter the frequency ratios and the relative amplitudes of the partials; there are several controls for this purpose. The Spread parameter, for example, will detune the upper harmonics in your model so that they become increasingly inharmonic, and the two Blur functions smooth out changes in either the individual amplitudes (Blur Levl) or frequencies (Blur Frq) of the sound''s spectrum. Though there is very little information in the manual about these two options, I found that I could use Blur Levl to increase or decrease the amount of vibrato in a vocal sample.

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FIG. 2: The Spectrum window toggles with the Sound Browser and has several display modes, including the 3-D waterfall view shown here.

Like some other current additive synthesizers (U&I MetaSynth comes to mind), Poseidon can extract data from a bitmap image file (BMP only on both the PC and the Mac) and use it to generate a new spectral model. The brightness of the image determines the amplitude of a frequency band, and the number of bands (calculated from 20 Hz to 20 kHz) depends on the number of partials you use in the resynthesis. There aren''t any controls to modify the image, but with a little luck, you''ll find an image that produces worthwhile results.

Even if the analysis produces garbage, however, you can tweak so many of the resynthesis playback parameters that you can turn most anything into a useful model. Changing the start position and playback speed, for instance, can have a huge impact on how the spectrum is scanned, and varying the loop mode (one shot, bidirectional, and so on) creates even more permutations of the resulting sound (see Web Clip 4).

Fans of microtuning will be pleased to know that Poseidon supports tuning setups in Scala format, and you can even give each voice (up to eight in normal playback mode or six in Unison mode) its own custom scale. Currently over 3,000 scales are available at the Scala Web site (, and with a bit of tweaking you can create your own.

In the Locker

Poseidon includes several banks of presets, and user contributions are already appearing on the company''s Web site. Moreover, each incremental upgrade that appeared during this review process also included new banks. Many of the sounds are clearly reminiscent of the VirSyn family and could probably have been created with Cube or Tera, but another very large portion is unique to Poseidon. Note that you can also map each bank to MIDI Program Changes, though there is no support for Bank Select messages.

Among my favorites is Flying Water, a shimmering, slithering sound that uses a bird model as its source. Raising the Blur Levl on the preset changes the sound into a colorful blast of steam (see Web Clip 5). Frost, from the Expressive category, loops bidirectionally over a very small slice of the spectrum to creates its haunting, evolving quality (see Web Clip 6), and Kreissaege uses a Tibetan cymbal as its source. I found that raising the Spread level to maximum on Kreissaege gave the sound an added edge (see Web Clip 7).

There are many sounds that would work as leads and pads, and searching for Film Music, World Music, Pop, or Jazz will point you toward dozens of presets, too. You''ll also find sounds reminiscent of granular synthesizers as well as more-traditional subtractive/analog emulations.

Some of the sounds—for example, Bass Drum and Analog Space—are less than inspired, but simply adjusting the Residual and Spread amounts can turn a dull preset into something more useful. Changing the filter that the preset uses can also have a positive (and dramatic) impact on a sound (see Web Clip 8).

Flowing Along

I spent most of my time with Poseidon in the Spectrum Editor, changing loop start points and adjusting the time the synth takes to play through different analysis files. By assigning MIDI controls to the various parameters, I could use the Mod Wheel to scroll through the analysis data, playing through a portion of the file and then freezing on a single frame (this can be set to occur automatically as well; see Web Clip 9). I also found the Blur controls, especially when combined with a bit of reverb, to be very useful for creating colorful, ambient timbres that layered well (see Web Clip 10).

You can record Poseidon''s output directly to disk in standalone mode (WAV only on the PC and AIFF only on the Mac) and of course when it is being used in a host. There aren''t any options to customize the interface (resizing or rearranging windows and controls, for instance), but you can change the overall color scheme using any of 17 different options.


Poseidon is more intuitive and somewhat scaled back from the complexity and multileveled architecture of Cube and Tera. And because it uses analysis/resynthesis as its main synthesis method, it has nearly unlimited potential for creating unique sounds, especially those that mix characteristics of two sources. I''d love to see even more ways to alter the analysis data, though. For example, it would be great if the program could adopt some of the spectral processing functions of Composers'' Desktop Project (, probably the most potent A/R toolkit around.

Poseidon''s documentation is on the slim side; there is little detail on any of the program''s features, and the getting-started-style explanations don''t go into much depth. You''re definitely in for a lot of trial and error with this one, though for many people that''s not a bad thing.

Poseidon also retains many of the quirks of other VirSyn programs, the most annoying of which is the lack of any undo function. Equally frustrating is the program''s failure to prompt you to save your presets after a work session, regardless of whether you have made changes or not. But these are things you''ll get used to if you work with VirSyn''s tools, and hopefully those features will be added to the company''s software someday.

If you''re looking to explore some new sonic territory, check out the trial version and listen to the Poseidon demos online. Just keep in mind that those only scratch the surface, and that the deeper you swim, the more you''ll get from Poseidon.

Associate Editor Dennis Miller is a composer and animator. Check out his work at

Web Clips: Listen to audio examples of presets, samples, patches, and more from the Poseidon software synthesizer