L'otary is not a simulated modulation effect plug-in; it's uses proper DSP coding designed to reproduce tremolo and vibrato--the Doppler-based sounds of the Leslie's Horn and Drum counter-rotating speakers.

There are cool graphics showing the speed (visually--a light bar showing 300 degrees of rotation) of the rotors and I liked that you have complete programmable independence between the Drum and Horn speakers--each with their own sections on the large GUI window.

Besides complete control over the virtual "mechanics" of the Leslie speaker, PSP L'otary includes the ability to adjust the individual microphones on the cabinet's Horn (high frequency speaker) and Drum (low frequency driver), their placement, EQ, gain and distance from the cabinet. These features and many others allow for other creative uses of this timeless effect.

There are separate Slow and Fast speed controls for setting the speed of the Chorale (slow) and Tremolo (fast) of the Horn and Drum with a master fader that changes them both together plus a stop button that stops the rotors according to the separate (ramp up and down) accelerate/decelerate speed values in Horn and Drum Inertia boxes. For example, you could have the Drum remain still for a super solid bass and have the Horn spin as usual. (Back in the day, I used to unhook the Drum's motor and rotated the speaker so it aimed at the microphone).

The Horn and Drum sections are separated by the Center section--a kind of global set of parameters for finishing sound. Here a single knob sets the amount of mechanical noises to simulate the quirky speaker's electric motors' mechanisms and wind noise. There are also controls to manipulate the audio power amplifiers driving the speakers--you can have no distortion at all or use the Drive control to saturate.

There is a 4-band EQ and a five-position Setup switch with five cabinet microphone configurations (positions) including mono. In addition, the Amp Only position turns off the speakers leaving just the sound of the amp--this allows L'otarty to be a mainstay saturation effect useful for anything you want the sound of an emulated tube amp. Lastly the three-control Ambience section places the speaker in an acoustic space.

I installed in my Pro Tools 11 HD rig and started inserting L'otary on every instrument to generate ideas. It was excellent on electric pianos--I preferred without the amplifier's color switched in. Any synth organ will sound very authentic and distorted guitars take on a nasty tone with the Leslie speaker's upper mid-range peakiness. I found the "relaxed" or "old rotary" presets good starting points to start tweaking rotating distorted guitar sounds.

Backing vocal pads (ahs) sound awesome and I found it was best to go with no amplifier at first and make sure the EQ section, cut-off frequency of the Horn, and the Ambience controls are checked and tweaked. Using Ambience produces an early reflection effect of the speaker's surrounding. L'otarty has a low CPU mode I found worked for 99% of the time but for backing vocals or lead vocals, I tried the Brilliant mode. It's subtle and a little better.

Lastly, the Setup choice of microphone placement makes a big difference in the stereo width. L'otarty is a stereo plug-in and has a mono-to-stereo instantiation that is just the thing for making point sources wider--just dial the L/R panned outputs to taste.

PSP's L'otary will become the standard rotary speaker plug-in because of its great sound and its intriguing and vast programmability. It is available for Windows and Mac OS X in VST, AU, AAX32/64 and RTAS plug-in formats and sells for $99 MSRP. I highly recommend it!