2023.03.15

doc/drums.txt

@@ -0,0 +1,82 @@
+Advamced Percussion Analysis
+in the Midistats Program
+
+This is an addendum to the midistats.1 file.
+
+The MIDI file devotes channel 9 to the percussion instruments
+and over 60 percussion instruments are defined in the MIDI
+standard. Though there is a lot of diversity in the percussion
+track, for most MIDI files only the first 10 or so percussion
+instruments are important in defining the character of the track. The
+program Midiexplorer has various tools for exposing the percussion
+channel which are described in the documentation. The goal
+here is to find the essential characteristics of the percussion
+track which distinguishes the MIDI files. This is attempted
+in the program midistats.  Here is a short description.
+
+-corestats
+Produces a line with 3 numbers separated by tabs. eg
+384	8349	448
+It returns the number of divisions per quarter note beat (ppqn),
+the number of note onsets in the midi file, and the maximum
+number of quarter note beats in midi file.
+
+-pulseanalysis
+Counts the number of note onsets as a function of its onset time
+relative to a beat, grouping them into 12 intervals and returns
+the result as a discrete probability density function. Generally,
+the distribution consists of a couple of peaks corresponding
+to quarter notes or eigth notes. If the distribution is flat,
+it indicates that the times of the note occurrences have not been
+quantized into beats and fractions. Here is a sample output.
+0.3496,0.0000,0.0000,0.1602,0.0000,0.0002,0.2983,0.0000,0.0000,0.1914,0.0002,0.0001
+
+-panal
+Counts the number of note onsets for each percussion instrument. The first
+number is the code (pitch) of the instrument, the second number is the
+number of occurrences. eg.
+35 337	37 16	38 432	39 208	40 231	42 1088	46 384	49 42	54 1104	57 5	70 1040	85 16	
+
+-ppatfor n
+where n is the code number of the percussion instrument. Each beat
+is represented by a 4 bit number where the position of the on-bit
+indicates the time in the beat when the drum onset occurs. Thus
+0 indicates that there was no note onset in that beat, 1 indicates
+a note onset in the beginning of the beat, 4 indicates a note onset
+in the middle of the beat, and etc. The function returns a string
+of numbers ranging from 0 to 7 indicating the presence of note onsets
+for the selected percussion instrument for the sequence of beats
+in the midi file. Here is a truncated sample of the output.
+
+0 0 0 0 0 0 0 0 1 0 0 4 1 0 0 4 1 0 0 4 1 0 0 4 1 0 0 4 1 0 0 4 1 4 4 0
+1 0 0 0 1 0 5 0 1 0 5 0 1 0 5 0 1 0 5 0 1 0 5 0 1 0 5 0 1 0 5 0 1 0 0 0
+1 0 5 0 1 0 5 0 1 etc.
+
+One can see a repeating 4 beat pattern.
+
+-ppat
+midistats attempts to find two percussion instruments in the midi file
+which come closest to acting as the bass drum and snare drum.
+If it is unsuccessful, it returns a message of its failue. Otherwise,
+encodes the position of these drum onsets in a 8 bit byte for each
+quarter note beat in the midi file. The lower (right) 4 bits encode the
+bass drum and the higher (left) 4 bits encode the snare drum in the
+same manner as described above for -ppatfor.
+0 0 0 0 0 0 0 0 0 0 33 145 33 145 33 145 33 145 33 145 33 145 33 145 33 145
+33 145 33 145 33 145 33 145 33 145 33 145 33 145 33 145 33 145 33 145 33 145
+33 145 33 145 33 145 33 145 33 145 33 and etc.
+
+-ppathist
+computes and displays the histogram of the values that would appear
+when running the -ppat. eg.
+bass 35 337
+snare 38 432
+1 (0.1) 64  32 (2.0) 8  33 (2.1) 136  144 (9.0) 8  145 (9.1) 136 
+
+The bass percussion code, the number of onsets, and the snare
+percussion code and the number of onsets are given in the
+first two lines. In the next line the number of occurrences of
+each value in the -ppat listing is given. The number in parentheses
+splits the two 4-bit values with a period. Thus 33 = (2*16 + 1).
+
+