I was drawn to Endless Series v3.1 because it it can produce different sounds from any other plugs I've tried. That being the ability to modulate Shepard tones. I've used it to create layers for scapes, or as an effect in my chain. Even by itself it makes interesting sound. There are six effect modes. The first two "tone" and "am sine" produce synthesis while the other four are effects to process incoming audio. One of effects is "am input" mode (amplitude/ring modulator) which I've had a lot of fun with, especially on drums. If you download the demo, I highly suggest that you try this. The last three are phaser, flanger, and filter.
One of the nice things about Endless Series is the "midi step" mode. This allows you to step through the cycles each time a note is pressed. One note is reserved to "reset" the cycles (C). This comes in very handy for sequencing, in any of the modes. You can get some great effects this way.
Bottom line - If you're into trying something different, give Endless Series a try. I'll bet you get some interesting results.
As some one interested in experimental music and sound design, Endless Series 3.1 is perfect! I believe that sheperd tones can be great for sound design and experimental music, as well as producing source material for swelling dance music(Trance and DnB in particular). Endless can also give drums great feel and effect, especially for breakbeats and theatrical/movie material. Endless's controls are very accurate and smooth but not to sensitive.
Endless Series is a unique high-quality sound mangler and generator, sound designers and film music producers should recognize the usefulness of this effect immediately.
Endless can make extremely cool and psychedelic flanging/phasing effects which are like nothing else on earth, it is fascinating to play with and listen to. I've found the effect works well on vocals, drums, synths, and especially guitars.
I haven't used the synth part directly, but it is helpful to familiarize one with the effect, and not only is investigating the psychoacoustic shepard tone effect educative and eye opening, but it's also fun!
You wouldn't know it from the plain looking UI, but it works in a very sophisticated way and feels extremely refined with many functional touches to help the user to control the effect. It can be used subtly as a treatment, or it can create it's own drama. This wide range and sophisctication of control makes using Endless a pleasure; so although it is unique, it is easy to discover potential uses for it and to imagine more.
As a plug-in developer myself, i know oli larkin is competent and capable to support his products; Endless is likely to be around in the future, and be maintained and improved. So I think Endless Series is a good buy, like a cool hardware stompbox. imo, if you like flanging/phasing type effects, or other worldly sound effects, you'll want to own Endless Series. And I think it is noteworthy that there is no other plug-in or hardware device like it.