Data AcQuisition And Real-Time AnalysisScope - Spectrum - Spectrogram - Signal Generator
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Sound Card Pitch Track Toolbox - Overview
Controls: Sgram/PT Dialog >> Pitch Track
When Spectrogram (Sgram/PT) is active, the Pitch Track Toolbox options are available by activating the Pitch Track button, which converts the color spectrogram to a real-time pitch tracker. Whereas the color spectrogram shows all spectral components, color-weighted by strength, Pitch Track shows only a single component: The spectral peak which is computed to be the pitch of the incoming signal.
This is a Toolbox, not a commercial instrument. There are many variables that affect the pitch tracking process, and this Toolbox allows you to explore them. Vocal analysis is easily done with Pitch Track, but live MIDI performance using your voice, whistle, or another instrument is likely to require some compromises and a great deal of practice... just like any instrument.
Pitch Track uses the Spectrum Track and Peak options to find the pitch. Use the Track Limits dialog button to set the detection threshold and frequency limits, as well as the optional Fundamental track mode. If Fundamental is off, only the largest peak is tracked. If Fundamental is on, the two or three largest peaks are assumed to include the fundamental and/or harmonics only.
Pitch Track only tracks a single voice or instrument at a time. Any other voices, including their strong harmonics, must be outside of the Track frequency limits, or else mistracking may result. (Harmonics of the tracked voice are OK, and may even be desireable in the Fundamental track mode since it can use them to help determine the fundamental.)
By default, the Pitch Track display background is a series of white (actually gray) and black horizontal bars that represent the "musical space" of the white and black keys of a piano or synthesizer keyboard. The current input pitch shows as a colored line at the corresponding note height, on the proper key bar. The color is related to loudness using the same palette and color scale as the normal color spectrogram.
Because black keys and white keys on a physical keyboard are the same musical size (one semitone), they are given equal size representations here. However, where two white keys are adjacent on a piano keyboard (B and C, or E and F), they are shown here as a double-wide bar. The screen is thus instantly recognizeable as a keyboard layout with the 2,3 pattern of black keys relative to white.
You can adjust how much of the keyboard is shown (and hence the size of the keys) by making sure that the eXpand button is active and using the eXpand Max and Min controls, which are duplicates of those in the X-Axis dialog. Alternatively, you can drag the Y-axis extents up or down, or use the horizontal scroll arrows at either end of the X axis.
Screen resolution is better (more expansion possible) at higher frequencies. With no expansion at all, the display covers about 9 octaves and the key bars are so small as to be nearly useless.
Note that Pitch Track eXpand state and limits are maintained separately from the normal Spectrogram. When you toggle Pitch Track on or off, the state and limits change accordingly.
The vertical axis is labeled to identify the octaves. C notes are always labeled, plus other notes as space permits at the given expansion. The octave number that appears after the note letter is based upon A4 = 440 Hz.
The trace normally maps the pitch frequency exactly as computed. Alternatively, the Step button causes the display to be quantized to the nearest exact note... a smooth sweep will show as a series of stairsteps.
The Hysteresis control allows you to make those steps "sticky", so that a pitch that is near the border between two notes doesn't jump back and forth. It can also be used to ignore mild vibrato. Very large values can be used with Note Bend to provide +/-2 octave tracking of continuous-tone instruments like violins or slide trombones.
The Pitch-to-MIDI button opens a dialog that allows you to "play" a MIDI instrument (synthesizer) using extracted pitch. The notes played are those shown when Step is active.
The +/-Octaves control allows Pitch Track to handle input frequencies that are beyond the 12.5 kHz MIDI range, such as the sounds of some insects, bats, or even steam leaks.
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