ReaTune (Cockos)

The three tab of the ReaTune plugin are:

Tuner - Displays the current note, useful for tuning other instruments.
Correction - Automatic Correction
Manual Correction - User corrects the pitch of individual notes by drawing on the graph

Tuner tab

Window size
Overlap
Reference
Note Display
Send MIDI events when pitch changes
Buffering mode
- Live input (lowest latency possible)
- Non-live input (lookahead - enables delay compensation for correction modes)

Automatic pitch correction

Key
- Name - A thru G#
- Mode
  - Major
  - Minor
  - Chromatic
  - Dorian
  - Phrygian
  - Lydian
  - Mixolydian
  - Locrian
  - Arabian
  - Egyptian
Notes Allowed - Allows the user to modify which notes are allowed in a specific key and mode
Attack Time - The time between the start of a note and when ReaTune starts to correct it if needed.
Stereo Correction - Enable or disable stereo correction
Pitch Shift Mode & Parameter - There are several modes available, each is best suited to different input signal types and each can be 'fine tuned' using the parameter drop down list. The parameters for each Pitch Shift Mode are not listed here.
- Project default - Just use the project default mode, no parameter drop-down list available.
- SoundTouch
- Dirac LE (slow)
- Low quality windowed (fast)
- élastique Pro
- élastique Efficient
- élastique SOLOIST
- élastique 2.1 Pro
- élastique 2.1 Efficient
- élastique 2.1 SOLOIST
Clear history
Click reduction (for some shifters, uses more CPU)

Manual pitch correction - Enable or disable manual correction
Track/update pitch graph - Update graph as REAPER plays
Prevent octave shifts - Unexpected harmonics in an audio signal can sometimes cause ReaTune to think the note as shifted up or down an octave, this option stops that - but sometimes you need it to be able to do that...
Prevent overlapping segments - As in the picture above, the segments (blue lines) are prevented from overlapping