Two identical LFOs are available as modulation sources in the mod pop-up menus.
The LFO (low frequency oscillator) signal is used as a modulation source. In an analog synthesizer, the LFO frequency generally ranges between 0.1 and 20 Hz, which is outside the audible frequency spectrum. Therefore, this type of oscillator is used only for modulation. The speed of the LFO in Ultrabeat can reach up to 100 Hz, which affords a number of possibilities that analog synthesizers don’t offer.
The parameters for both Ultrabeat LFOs are described below. You can adjust LFO 1 and LFO 2 independently of each other.
LFO 1/2 buttons: Select the corresponding LFO, allowing independent parameter adjustments.
On/off button: Turn the selected LFO on or off.
Sync/free buttons: The LFO speed can be synchronized with the Logic Pro X tempo or set independently. Click either button to activate the corresponding mode.
Rate knob and field: Rotate to set the speed of the LFO. Depending on the Sync/Free setting, the rate is displayed in Hertz or rhythmic values—the latter when tempo synchronization is active. Rates range from speeds of 1/64 notes to a periodic duration of 32 bars. Triplet and punctuated values are also available.
Waveform shape slider: Drag to determine the shape of the LFO waveform. The shape updates in the display.
Cycles knob and field: Rotate to set the number of times the LFO waveform repeats.
Ramp knob and field: Rotate to set the time it takes for the LFO modulation to fade in or fade out. The Ramp value is displayed in milliseconds.
Rotate Ramp to the right to set the LFO fade-in time.
Rotate Ramp to the left to set the LFO fade-out time.
At the middle position, Ramp has no effect on the LFO.
Drag the Waveform Shape slider from left to right to morph the waveform from a triangle, to a sawtooth, sine, square, and finally a rectangular wave shape—including all variations in between. At the far right position, the LFO produces random waveforms.
The graphical display shows the current LFO waveform shape.
The table outlines how different waveform shapes can affect your sounds. Intermediate waveform shapes result in hybrid waveforms and hybrid behaviors.
Waveform | Comments |
|---|---|
Triangle | Well suited for vibrato effects |
Sawtooth | Well suited for helicopter and space gun sounds. Intense modulations of oscillator pitch with a sawtooth wave lead to “bubbling” sounds. Intense sawtooth modulations of lowpass filter cutoff and resonance create rhythmic effects. |
Sine | Ideal for smooth, even modulations. Its position on the Waveform Shape slider enables you to smoothly morph between sawtooth and square/rectangular waves. |
Square and Rectangle | Square/rectangular waves periodically switch the LFO between two values. The right hand rectangular wave switches between a positive value and zero. The left hand rectangular wave switches between a positive and a negative value set to the same amount above/below zero. |
Sample & Hold | The right hand waveform outputs random values. A random value is selected at regular intervals, as defined by the LFO rate. Use a random modulation of oscillator pitch to generate an effect commonly referred to as a random pitch pattern generator or sample and hold. Play very high notes, at high LFO rates and high intensity—you’ll recognize this well-known effect from hundreds of science fiction movies. The term Sample & Hold (S & H) refers to the procedure of taking samples from a noise signal at regular intervals. The values of these samples are then held until the next sample is taken. |
An LFO normally oscillates continuously. On percussive signals it can, however, be interesting to limit the LFO cycles (repetitions of the entire waveform) to a defined number. Ultrabeat enables you to set the number of LFO cycles with the Cycles parameter. After completing the defined number of cycles, the LFO stops oscillating.
Rotate the Cycles knob to set the number of LFO waveform cycles. The range of Cycles parameter values extends from 1 to 100. The Cycles parameter can also determine whether the LFO waveform is started from the beginning, at a zero-crossing point, with each note trigger, or continues oscillating.
A Cycles value of 1 allows the LFO to function as an additional, very basic, envelope generator.
Set Cycles to its maximum value (full right position) for an infinite number of cycles (standard LFO behavior). The LFO is not reset by incoming MIDI note-on messages.
When Cycles is set to values under 100, the LFO is reset by each new MIDI note-on message (Note On Reset).
Your choice to trigger an LFO cycle from the same spot or to allow it to oscillate freely, regardless of phase, should be based on the needs of the sound. The random element of free-running LFOs can make many sounds richer. This, however, can be at the expense of a percussive attack—which is generally inappropriate for drum sounds.
Tip: Try small Cycles parameter values, with the LFO source used to control the Volume (Level) of one or both oscillators. This results in drum flams or hand claps. You can also use minor shifts of the LFO phase, with the Cycle value set to Infinity, to add an analog character to a drum sound.