Overview

This module implements a pair of low frequency oscillators, along with a scope for viewing either of the individual LFO waveforms, or their mix. This module has three outputs, one for each LFO, and a third output with a mix of the two LFOs. Like the single LFO module, this module is ideal for generating interesting variations within a musical part.

Each LFO has a choice of five waveforms: Sine, Square, Sawtooth, Triangle, and Sample & Hold. These basic waveforms can be modified by several parameters: Pulse Width (works for all waveforms), Starting Phase, Hard Sync, Rectify and Invert. Also, each waveform can be manually reset or muted.

In addition, all of these parameters can be used as modulation targets via the ParamMod. module This vastly increases the potential shapes that can be created. For instance, an LFO can be reset on a random basis by using ParamMod from a Modulation Sequencer with a random pattern.

Control over the frequency of each LFO is designed to be music-friendly. There is a choice of four different units of measurement: Hertz, sixteenth notes, beats and bars. For each of those choices the frequency (or period, as appropriate), can be set to a value from 1 to 100.

The mix output of the two LFOs can be set to either be a normal mix (the signals are added), or the multiplication (ring mod) of the two.

Any of the three outputs for this module can be monitored using the built-in scope. The vertical range of this scope is fixed at [-1, +1], so when mixing waveforms, it is possible that the value will move beyond the range of the scope.

The base value range of each LFO is [-1, +1]. This can be reduced using the 'Lvl' control. To scale the output to wider ranges, use a SignalProc module.

Techniques

The most obvious use of this module is in conjunction with the ParamMod module to modulate parameters in other Numerology modules, including Audio Unit parameters. For detailed steps on how to set that up, see the documentation for that module. There are a number of other options worth exploring also:

• Use the Dual LFO in conjunction with CC, NRPN, or PitchBender modules to generate MIDI automation data for your hardware synths. Using a slowly moving LFO (usually 16 bars) over filter cutoff or other timbral parameter of a synth is always a useful way to animate a mix.
  
  
• Use a SignalProc module to re-scale the output of an LFO to semitone ranges (+/- 12, 24, or 48) and use it as a pitch source.
  
  
• You can use LFOs to generate gate signals as well, just remember that a gate is on when the LFO is > 0, and off when the LFO is <= 0.

Parameters

Mutes the output of the LFO. This is a true mute, not an on/off switch, so the LFO keeps running when muted.

Resets the LFO to its starting phase value.

Chooses the waveform used by the LFO. To emulate a ramp, invert the saw wave.

Sets the base unit used to set the frequency of the LFO.

For a Hertz base unit, sets the frequency of the LFO from 1 to 100 Hz. For a music-based time period (1/16, beat, bar) sets the period of the waveform -- the amount of time before it repeats.

Scales the output level of the LFO

Controls the ratio of the amount of time a waveform spends above 0, vs. the amount it spends below zero. This works for all waveforms, and is a good way to vary the shape of a waveform.

Sets the starting phase of the waveform in degrees (0-360). This param allows you to have a waveform start at some value other than the default, which is 0 for all waveforms except the sawtooth.

This param works just like it does for sequencers: it resets the waveform every X beats. Very handy for getting complex waveforms to repeat at regular intervals.

This performs an absolute value operation on the LFO output, so all negative values are moved to positive values.

Inverts the output of the LFO.

Controls whether the LFO Mix output is a regular mix ('Add') or ring mod ('Mult') of the two LFOs.

Chooses which LFO output of the module to monitor on the scope.

Advanced Parameters

These parameters are accessible by opening the Advanced Settings panel of the module, just click on the little triangle icon in the lower-left corner of the module.

This determines whether the LFO runs automatically or manually. When set to "auto", it will run when the master clock runs, when set to "Manual", you have to start and stop the LFO manually using its Play/Stop controls.

This determines how the two internal LFO's are mixed together. By default, their value are added, but in some cases, it is more useful to multiply them together.

Ports

This is the clock input for the module, it must be set or the LFO will not run.

This is a direct CV output LFO A.

This is a direct CV output LFO B.

This is the mixed output of both LFOs.