Processing : Event Operations : Grid Quantize : What to Quantize

What to Quantize
The What to Quantize settings determine what aspects of any selected MIDI notes are quantized: Note Ons (attacks), Note Offs (releases), or both. You can also select whether to quantize audio clips or Elastic Audio events. Depending on what type of track material is selected, not all options will be available. If only MIDI is selected, the Audio Clips and Elastic Audio Events options are unavailable. If only audio is selected, the Note On, Note Off, and Preserve Note Duration options are not available.
Note On
When selected, MIDI note start points are quantized.
Note Off
When selected, MIDI note end points are quantized.
Preserve Note Duration
When selected, MIDI note durations are preserved.
When deselected with the Note On option selected, note end points are not moved.
When deselected with the Note Off option selected, note start points are not moved.
If the options for both Note On and Note Off are selected, the Preserve Note Durations option is unavailable.
The following figure shows how MIDI notes are adjusted by the different What To Quantize options.
 
Before quantizing, followed by two examples showing the results of different What To Quantize settings
Audio Clips
When selected in the What to Quantize pop-up menu, Quantize is applied to clip start times (or sync points if present) for selected audio clips. MIDI clips are not affected. Typically, you will only want to apply quantization to sliced audio clips or clip groups (such as imported REX files or clips created using the Separate Clips at Transients command or Beat Detective). Quantization can be applied to mixed selections of MIDI notes and audio clips.
Elastic Audio Events
When selected in the What to Quantize pop-up menu, Quantize is applied to detected transient events within the Edit selection on Elastic Audio-enabled tracks. Quantization can be applied to mixed selections of MIDI notes and Elastic Audio events. Warp markers are created automatically on top of Event markers nearest the quantize grid. Quantize then uses these Warp markers to apply quantization.