BiFilter is a filter plug-in currently avaible in PC VST for from Tone2. This is a review of the new version 1.61. As a quick explanation for those unfamiliar with the effect, it’s normally used to add or subtract frequencies, like a single band of an EQ, but can do much more and also forms a huge part of the sound of so many synthesizers and defines much of electronica. The BiFilter manual explains it in more detail.
Tone2 is comprised of Markus Feil and Dr. Hartmut Pfitzinger. Several of you may be more familiar with Markus Feil from reFX (most notably Slayer 2, Vanguard and the discontinued JunoX) though a quick glance at Tone2 website reveals other projects as well. With that sort of background, you’d expect BiFilter to be a well-put together product. What you might be surprised by is that such a well-put together product would be free. I’m guessing this is to encourage users to upgrade to its big brother, Filterbank 2. Nonetheless, BiFilter feels like a powerful commercial plug-in in it’s own right, even side-by-side with competing products costing as much as $200 U.S.
Though it’s described as a filter unit, and the 45 included filter modes certainly attest to that, there is also an output stage with ”seven” distortion modes. I put that in quotes because one of the seven is actually a neutral volume control. This is a LOT of filter types to be able to work with, especially with the included distortion effect. I won’t go into listing them all, since the official list is comprehensive (though the manual still needs to be updated to include them all). I’ll simply say that it’s very versatile and includes everything from the bread and butter lowpass and highpass to more unusual filters such as AM, FM, formant/vocal, phasing and more.
Luckily, the type of filter or distortion effect can be quickly selected either through a drop-down list or cycled through with up-down arrows next to the display name. BiFilter has a straightforward, simple and easy to use interface that’s easy on the eyes. There is also an included set of presets to quickly try out all the different types, though the interface is so straightforward that plug-in can be explored almost as easily without them. This is partially because you won’t find any more advanced complicated options like LFOs or envelopes here, though many of them can be found on BiFilter’s big brother FilterBank 2.
The installation is straightforward through a setup program and the only thing a user needs to know is their VST plug-in directory. However, it would have been helpful to be able to view the manual or a readme file of some sort before installing since the manual can only be accessed by opening it in the installation directory. The manual starts off with a brief explanation of the product, followed by usage and then a reference section. It covers the concepts of filtering are first and the list of filter types in the application next. The manual needs to be updated and appears to be based on an earlier version so it doesn’t address about half the filters. Those that are addressed have meaningful short explanations that help to differentiate between them even before you start listening. This is really nice considering how many filters there are but I would like to see the manual brought up to date as soon as possible. The manual also covers useful information about automating via MIDI CC or through your host’s VST automation system.
Now all the variety in the world wouldn’t mean a thing if the sound quality weren’t there. This is not the case. It’s there and it’s there in spades. With such a wide range of variants, users are almost guaranteed to find one that fits their tastes. BiFilter can do everything from straightforward shaping to resonance heaven and everything in between without batting an eye. It can make basslines sound fat or squelch with resonance or be used with automation to create interestingly varying textures. No matter what you throw at it, it’s ready.
The effectiveness with which a software filter can emulate a smooth response as you sweep the ”cutoff” (the frequency response point) from one point to another can result in a so-called ”stair-step” effect when interpolation from one frequency to another isn’t smooth. Think of it like the way animation or film clips mimic motion vs. a slideshow. The better this is handled, the more it comes across seamlessly (like a movie) whereas a poor emulation is more like a somewhat fast slideshow, with each picture being noticed more than the motion. I’m happy to say that BiFilter handles this very smoothly and didn’t notice any stair-step effect.
I’ve been working with software filters since the end of the 90s and I was still extremely impressed by BiFilter. If you have a PC and a VST host you really should check it out and since it’s free you have no excuse not to. Make this the first filter you try. I look forward to seeing more from Tone2 in the future.