The main operational difference is that for v4 effect onward, the
sound name will now be *TRACK*. This will not affect existing
effects since they use version number 3 or less.
This also provides the Nyquist effect with much more information about
the current processing:
Variable Property What
*AUDACITY* VERSION current Audacity version number
*SYSTEM-DIR* BASE Audacity install path
*SYSTEM-DIR* DATA Audacity data path
*SYSTEM-DIR* HELP Audacity help path
*SYSTEM-DIR* TEMP Audacity temp file path
*SYSTEM-DIR* PLUGIN Audacity search path for Nyquist plugins
*PROJECT* RATE current project sample rate
*PROJECT* TRACKS total number of tracks in the project
*PROJECT* WAVETRACKS number of wave tracks in the project
*PROJECT* LABELTRACKS number of label tracks in the project
*PROJECT* MIDITRACKS number of midi tracks in the project
*PROJECT* TIMETRACKS number of time tracks in the project
*SELECTION* START start time of current selection
*SELECTION* END end time of current selection
*SELECTION* TRACKS number of tracks in the current selection
*SELECTION* CHANNELS number of channels in the current selection
*SELECTION* LOW-HZ low frequency from spectrogram (if available, else nil)
*SELECTION* CENTER-HZ center frequence (calculated) (if available, else nil)
*SELECTION* HIGH-HZ high frequence from spectrogram (if available, else nil)
*SELECTION* BANDWIDTH bandwidth in octaves (calculated) (if available, else nil)
*SELECTION* PEAK-LEVEL peak amplitude for the current selection
*TRACK* INDEX 1-based index of track being processed
*TRACK* NAME name of track
*TRACK* TYPE type of track: wave, midi, label, time
*TRACK* VIEW track view: Waveform, Waveform (dB), etc.
*TRACK* CHANNELS number of channels in the track
*TRACK* START-TIME start time of track
*TRACK* END-TIME end time of track
*TRACK* GAIN track gain
*TRACK* PAN track pan
*TRACK* RATE sample rate of track
*TRACK* FORMAT sample format: 16 (int), 24 (int), 32.0 (float)
*TRACK* CLIPS list of start/end times for clips for each channel
