Logic Pro Alchemy formant filter controls

Source components are shown only in advanced view. Click the Advanced button to switch to advanced view, then click the A/B/C/D button to select the source you want to edit.

The parameters in this section are shown when the Formant button is active in an additive or spectral source subpage.

When audio is imported into the additive or spectral engines with the Formant option enabled, the signal is analyzed and resonances in the original signal are extracted and converted into a formant filter shape. See Logic Pro Alchemy Import browser.

The formant filter scales the amplitude of additive partials or spectral bins over time to recreate the characteristic resonances of the instrument, rather than processing the audio signal like a conventional filter.

Formant filter analyzed parameters

The analyzed controls work only if you enable the Formant button in the Import browser when importing your audio files. This more detailed analysis attempts to determine the resonant frequencies of the source audio data.

On/off button: Enable or disable the analyzed formant section.
Shift knob: Shift the formant filter up or down in semitones. Higher values can make sounds seem brighter or thinner. Lower values can create a darker, thicker character.
KTrack knob: Determine how the formant filter tracks notes on the keyboard. At 100%, filter resonances shift up or down in pitch with the note. Set to lower values to reduce key tracking which may make some sounds playable over a wider keyboard range.
Size knob: Stretch the formant filter to change the perceived size of the resonant chamber. Use this parameter to alter the size of a guitar body or to make a child’s vocal sample sound like that of a giant, for example. The Size knob works in conjunction with the Center parameter.
Center knob: Set the center frequency for formant stretching (controlled with the Size knob). Resonances below the center frequency are shifted upward as the Size knob value is increased. A corresponding downward shift occurs to resonances above the center frequency.
Note: The Center knob has no effect when the Size knob is set to 100%.
Smooth knob: Set the rate of change for the formant filter. High values smooth and slow down formant changes. Low values exaggerate and speed up changes. Low values can also introduce an unusual “chattering” distortion that may be suitable for drum sounds.

Formant filter synthesized parameters

The synthesized controls work with any additive or spectral material and do not require the formants to be analyzed on import. Use these parameters to impose new resonant characteristics on the original signal. The default settings provide a range of vowel sounds: use the Select knob to morph through the default “a,” “e,” “i,” “o,” and “u” vowel sounds loaded into the four slots to the right.

On/off button: Enable or disable the synthesized formants section.
Shift knob: Shift all synthesized formant filters up or down in semitones. Higher values can make sounds seem brighter or thinner. Lower values can create a darker, thicker character.
Size knob: Stretch the formant filter to alter the perceived size of the resonant chamber. Size works in conjunction with the Center knob.
Center knob: Set the center frequency for the formant stretch set with the Size knob. Resonances below the center frequency are shifted upward as the Size value is increased. A corresponding downward shift occurs to resonances above the center frequency.
Select knob: Morph smoothly through the four filter units. The displayed value indicates position. Whole numbers indicate a particular filter unit, and fractional values indicate a position between filters.
Filter type pop-up menus and fields: Choose the filter type used in each of the four formant filters. You can step through the available filter types with the Previous and Next buttons (the arrows).
- Off: Passes the original data, as if the synthesized section were turned off. Assign this type to use one of the four filter units as a bypass. Adjust the Select knob to quickly disable synthesized formant processing.
- Comb filters: Comb filters are so-named because they create a distinctive comb-like pattern of boosts and cuts in the frequency spectrum, arranged in a harmonic series.
  - Comb Neg: The position of the first harmonic is determined by the Shift knob. The Size knob can be used to stretch the pattern of cuts and boosts up or down the frequency spectrum, or both, depending on the setting of the Center knob. The negative filter name is used because it recreates the effect of a phase-inverted delayed signal that boosts only odd harmonics, resulting in a hollow sound.
  - Comb Pos: This filter emulates the effect of mixing in a positive phase delayed copy of the original signal, resulting in a boost of both even and odd harmonics. This filter has a brighter sound than the negative comb filter.
  - Metal Combs: The Brass, Iron, Steel, and Tin comb filter variants provide a distinctive tonal coloration that emphasizes different harmonics in the frequency spectrum. To help you visualize these differences, the “teeth” (harmonics) on the comb are of varying thicknesses and are spaced at different intervals in each filter. Experiment with each comb to determine the best choice for your sound.
- Classic and Parallel filters: The classic variants are two-pole designs. The parallel filters are multipole designs.
  - Band Pass: A bandpass filter with a gentle slope. Signals above or below the set center frequency are attenuated.
  - High Pass: Emulates a two-pole highpass filter that gently reduces the levels of lower frequencies. The Shift knob sets the cutoff frequency. The Size knob changes the filter slope.
  - Low Pass: Emulates a two-pole lowpass filter that gently reduces the levels of higher frequencies. The Shift knob sets the cutoff frequency. The Size knob changes the filter slope.
  - Notch: A filter that attenuates a narrow band of frequencies near the set frequency. The frequency band can be moved up or down the frequency spectrum with the Shift knob. The Size knob sets the width of the band (notch).
  - Peak: A filter that boosts a narrow band of frequencies around the set frequency. The frequency band can be moved up or down the frequency spectrum with the Shift knob. The Size knob sets the width of the band.
- Vowel Bright, Classic, and Smooth filters: Bright vowel sounds contain more high frequency content and are the most aggressive-sounding. Classic vowel sounds are warmer, and are similar to synthesizer vowel sound filtering. Smooth variants are more natural-sounding vowel shapes with a gentler filter slope.
  Tip: Most of the “vowel” filters are not strictly designed to create that exact vowel. Each Bright, Classic, and Smooth vowel filter is more of a unique variation on that general sound, with not only brightness differences, but also overall character differences. Additionally, any vowel filter can be independently modulated, alone or in conjunction with Select knob morphing between filters (even from mismatched sets). Use these facilities to dramatically expand your filtering options.
  - Vowel A: Mimics a set of vocal chords to impose an “a” vowel sound on the audio. Each variation of this complex filter shape has prominent peaks at different frequencies. It is, generally speaking, an open-sounding filter.
  - Vowel E: Mimics a set of vocal chords to impose an “e” vowel sound on the audio. Each variation of this complex filter shape has prominent peaks at different frequencies. It is, generally speaking, an open-sounding filter.
  - Vowel I: Mimics a set of vocal chords to impose an “i” vowel sound on the audio. Each variation of this filter shape has prominent upper midrange peaks and a further low-mid peak, making this filter sound thinner and less open than the “a” and “e” vowel filters.
  - Vowel O: Mimics a set of vocal chords to impose an “o” vowel sound on the audio. This filter shape has gentler midrange and upper midrange peaks with a dominant low-mid resonance. The result is a rounder sound with less brightness and presence than the vowel types above.
  - Vowel U: Mimics a set of vocal chords to impose a “u” vowel sound on the audio. This filter shape has gentler midrange and upper midrange peaks with a prominent low-mid resonance. The “u” filter variants also emphasize higher-range content around 7 and 8 KHz, for example, making them sound thinner than the “o” filter.

Modify formants in a resynthesized additive guitar sound

In Logic Pro X, from the Name bar, click the File button and choose Initialize Preset from the pop-up menu to reset all Alchemy parameters to default settings.
Select source A, then click the source select field and choose Import Audio from the pop-up menu.
In the Import browser window, click the Additive and Formant Import Mode buttons.
Navigate to the Guitars subfolder in the Factory samples folder, and choose a single guitar sample.
When loading is complete, click the Formant button to the right side of the source A window. Note that the upper Analyzed section is turned on.
Adjust the Shift knob to move resonances up or down in frequency and to change the timbre. Small amounts of Shift variation work well for subtle changes: try a few semitones in either direction.
Play some very low notes, then some very high notes. Gradually turn down the KTrack knob to reduce key tracking for the formant filter, and note the difference when you replay the high and low notes.
Adjust the Size knob value to change the apparent size of the guitar body. Also adjust the Center knob value, and note the effect it has on the tone of the resulting larger or smaller guitar body.

Modify formants in a resynthesized spectral drum loop

In Logic Pro X, from the Name bar, click the File button and choose Initialize Preset from the pop-up menu to reset all Alchemy parameters to default settings.
Select source A, then click the source select field and choose Import Audio from the pop-up menu.
In the Import browser window, click the Spectral and Formant Import Mode buttons.
Navigate to the Loops subfolder in the Factory samples folder, and choose a drum loop.
When loading is complete, click the Formant button to the right of the source A window. Note that the upper Analyzed section is turned on.
Adjust the Size knob value to make the drums seem bigger or smaller.
Adjust the Smooth knob value to alter the rate of change for the formant filter. Higher values smear the timbre of one drum into the next. Lower values exaggerate changes and create an unusual distortion near the bottom of the knob range.

Create a talking additive sound with synthesized vowel formants

In Logic Pro X, from the Name bar, click the File button and choose Initialize Preset from the pop-up menu to reset all Alchemy parameters to default settings.
Select source A, then turn off the oscillator in the VA section to the right.
Click the Additive button, and turn on the additive section. You will hear an additive sawtooth sound if you play some notes.
As an option, increase the Num Partials value. This helps to prevent the sound becoming dull if played in lower registers.
Click the Formant button, and turn on the lower Synthesized section. Play a few notes to hear the “a” vowel sound that is imposed on the sawtooth wave.
Increase the Select knob value, and play a few notes. Note how the vowel sound morphs to an “e,” then an “i,” then finally a “u” at 100%.
Reduce the Select knob value, then modulate it with a new AHDSR envelope (AHDSR2), and leave the depth at +100%.
Set Sustain to zero for the AHDSR2 envelope. Note the “yeah” articulation this creates as you play each note.
Increase the Attack time for the AHDSR2 envelope. Note the “aya” type articulation this creates as you play each note.
Adjust the Shift knob, the Size knob, and the Center knob, to explore the different timbres available.
Switch the order of vowels in the four pop-up menus, and also load different filter types such as Comb.

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Logic Pro X User Guide