Key Tracking LFO Frequency Cheat Sheet: Values Matching the Oscillator Frequency

[vlzs]

• These are cheat sheets for referencing the LFO Frequency values that establish the octave relationship between the Mai Tai LFO, which is set to Key(Key Tracking), and each oscillator at 2', 4', 8', 16', and 32'.
• When using Key Tracking LFO for AM(Amplitude Modulation), these cheat sheets are handy.
• (The LFO and Oscillator gradually drift out of sync over time because the LFO Frequency value is rounded.)
• 
• 

Setting OSC to -3 semitones aligns the phase of the LFO and Oscillator.

• By setting the oscillator frequency to a simple integer value, the LFO can follow at divisible values.
• However, since the transpose setting differs from other presets, it can be inconvenient when exploring presets.
  • For example, when exploring presets to replace sounds used in a song, you might find a preset with a pitch that's off-key from the song's key.
• 
  
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[Craig Anderton]

It seems this would also be useful for basic FM synthesis?

 

[vlzs]

It was useful on AM, but not on FM.

• In AM, LFO - Frequency shifts harmonic series
• In FM, Modulation Amount shifts harmonic series
• Therefore, it is necessary for AM but not used for FM.
• (Or perhaps there's a use I haven't discovered yet)

The values used to generate the harmonic series in FM

• 

Frequency modulation generates harmonic series like this, for example.

• 
• The frequency difference between Partials is the same as LFO - Frequency.
  • 
  • This is a harmonic series based on the fundamental frequency of the LFO.
• Adding the fundamental creates a harmonic series like that produced by an oscillator.
  • 

I tried with Mai Tai

• harmonic series generated with frequency modulation.preset
  • Download → https://scrapbox.io/files/696899ba9ff5081869785e3e.preset
• 
  • The note being played is C3.
• Added Fundamental using OSC2
  • fandamental added.preset
    • https://scrapbox.io/files/696899bdc1953c6d428148d4.preset
  • 
    • The note being played is G2.

 

[vlzs]

Coming back to this old thread — I think my earlier reply came across as a bit blunt. To be honest, I wasn't fully sure of the answer myself, and I should have said so instead of stating it so flatly. Sorry about that. I can’t look into it right now, but I’ll look into it further when I have some time.

 

[Craig Anderton]

I can’t look into it right now, but I’ll look into it further when I have some time.

Thanks for circling back. Mai Tai is useful for FM because it's one of the few synthesizers where LFOs can go into the audio range. I wrote about this for the PreSonus blog, but it and many more of my blog posts were removed for some reason. But if you have my Fender Studio Pro tips ebook, there's an updated version of the blog post starting on page 742 (along with some downloadable files and audio examples). The tip's introduction gives a good idea of what's covered:

FM synthesis uses one or more oscillators in the audible range to modulate one or more other oscillators’ pitch. Mai Tai can create FM sounds because the LFOs go up to 8 kHz, which provides additional audio oscillators. The LFOs also track keyboard pitch, so sounds are consistent across the keyboard. Furthermore, LFO 2 can modulate LFO 1’s frequency, which allows for 2-operator FM synthesis.

Here's a description for the most basic FM synthesis presets:

Osc 1 and Osc 2 are layered. LFO 1’s sine waveform is in the audio range, and tracks the keyboard. For modulation, LFO 1 modulates Osc 1 to create frequency modulation. Vary the LFO 1 Rate control in the audio range to change Osc 1’s timbre via FM synthesis. Then turn off Osc 2, and vary the LFO 1 Rate control to hear a variety of bell and chime-like effects. For instant ambient sounds, add delay and reverb.

One additional tip for Mai Tai FM synthesis is that either the 80s or Normal quality settings work best. Oversampling with the High or Supreme settings adds more unpredictability because of the higher bandwidth.