Sculpture LFO waveforms in Logic Pro for iPad
The LFO Waveform pop-up menus set different waveforms for the LFOs. The table outlines how these can affect your modulations.
Waveform | Comments |
---|---|
Sine | Ideal for constant, even, modulations. |
Triangle | Well-suited for vibrato effects. |
Sawtooth | Well-suited for helicopter and space gun sounds. Intense modulations of the oscillator frequencies with a negative (inverse) sawtooth wave lead to “bubbling” sounds. Intense sawtooth modulations of lowpass filter cutoff and resonance create rhythmic effects. The waveform can also be inverted, resulting in a different start point for the modulation cycle. |
Rectangle | Use of the rectangular waves periodically switches the LFO between two values. The Rectangle Unipolar wave switches between a positive value and 0. The Rectangle Bipolar wave switches between a positive and a negative value set to the same amount above and below 0. An interesting effect can be achieved by modulating pitch with a suitable modulation intensity that leads to an interval of a fifth. Choose the upper rectangular wave to do this. |
Sample & Hold | The three Sample & Hold (S & H) waveform settings of the LFOs output random values. A random value is selected at regular intervals, as defined by the LFO rate. The S & H waveform steps between randomized values (rapid switches between values). The S & H Lag setting smooths the random waveform, resulting in fluid changes to values. The S & H from CtrlA setting is controlled by the CtrlA modulation source. For example, you could assign aftertouch as the CtrlA source to trigger S & H modulation of pitch. The term Sample & Hold 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. Tip: A random modulation of pitch leads to an effect commonly referred to as a random pitch pattern generator or sample and hold. Try using very high notes, at very high rates and high intensities—you’ll recognize this well-known effect from hundreds of science fiction movies. |
Filtered Noise | Can be used for chaotic modulations, but it is principally of use in conjunction with the LFO envelope function, where you would introduce a brief modulation at some point in the note phase—for example, to introduce breath in a brass emulation, or to control an organ key click or piano hammer noise. The random nature of the noise waveform means that such modulations would vary slightly each time. |
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