10.6

35Logic Pro Instruments
Note: The additive engine processes partials in groups of four. Set the Num Partials
parameter to a multiple of four to achieve the best compromise between CPU load
and sound quality. Always set Num Partials to the lowest number of partials that are
required by the sound because this helps to reduce CPU load.
• PVar knob: Tune all partials simultaneously. This occurs before processing by the
additive effects modules which stretch/shift partial tunings. Set to 0% to tune all
partials in a perfect harmonic series. Set to 100% to make each partial follow the pitch
fluctuations detected in the original audio file. The sonic impact of this parameter is
highly dependent on the audio material: sounds with strong inharmonic content such as
bells are dramatically changed by reducing pitch variations. If all partials are tuned to
the harmonic series, however, the knob has no influence on the sound.
The pitch variation knob is most useful when dealing with resynthesized audio. For
example, if you analyze a vocal sample recorded with vibrato, this knob lets you reduce
the vibrato depth, or remove it entirely with a setting of zero. Removing all pitch
variations from a vocal can result in a synthetic, artificial character.
• Sym knob: Alter the symmetry, or shape, of sine waves by lengthening the first half of
the waveform while shortening the second, or the reverse. The audible effect is similar
when the knob is turned in either direction. Symmetry alters waveforms until they are
no longer pure sine waves in shape, resulting in each partial developing independent
harmonics and making the sound brighter.
Resynthesize a sound and modify it with the main additive controls
1. In Logic Pro, 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.
2. Click a source select field, then choose Import Audio from the pop-up menu.
3. In the Import browser, click the Additive button to change the analysis mode.
4. Choose an audio file, then click Import.
Single notes with a strong harmonic character tend to work well. A good source of such
files is the Vocals subfolder of the Factory samples.
5. Play the file up and down the keyboard and reduce the value of the Num Partials knob
to remove upper harmonics. Note that when playing higher notes you will need to turn
this knob down further before you hear it start to take effect.
6. Reduce the PVar knob value to remove all pitch variations and force all partials to a
perfect harmonic series. A PVar value of zero completely removes any vibrato or pitch
changes in the source sound.
7. Adjust the Sym knob value to change the symmetry of source sine waves, and note the
extra brightness that is introduced by new harmonics that are generated.