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abcmatch

NAME

abcmatch - search sequences of notes in an ABC file

SYNOPSIS

abcmatch data-file [number] [-a] [-br d] [-c] [-con] [-ign] [-length_hist] [-pitch_hist] [-qnt] [-r n] [-v] [-ver]

DESCRIPTION

abcmatch searches an ABC file containing (potentially) many tunes for specific sequences of notes. For example, if you know a few bars of a tune, you can use this program to find the tune having this sequence and perhaps identify the tune.

At a minimum, abcmatch requires two files. A template file called match.abc which contains the bars that you are searching for and a large file consisting of a hundred or more ABC tunes. The program automatically loads up the match.abc file and then scans every tune in the large file.

Though the program can be run stand-alone, it is really meant to be run with a GUI such as runabc.tcl (which is not yet part of Debian). Most of its output is rather cryptic.

THE MATCHING PROCESS

The template file must be a well-formed ABC file containing the basic X:, M:, L:, and K: headers as well as the bars to be matched. (Normally, this file is created by runabc.tcl.) It is important to finish each bar in the match file with a vertical line.

abcmatch uses the key signature to figure out the relative position of the notes in the scale, and to determine all the assumed sharps and flats. Therefore the program can find matching bars in a tune that has been transposed to another key, as long as the key difference is not too large. Matches are output in a list format looking like

29 30 4
30 31 4

Each line indicates a particular match found by the program. The first number on each line gives the relative position of the tune in the data-file, while the next number gives the X: number of that tune. The last number is the bar number of the matching tune. Bar numbers are counted sequentially from the start of the tune, and all V: and P: indications are ignored. That is, the bar number returned by abcmatch may not match bar numbers printed by one of the PostScript-producing ABC processors such as abcm2ps or abcmidi-yaps.

For the purposes of matching, abcmatch ignores all guitar chords, lyrics, note decorations (e.g., staccato markings), grace notes, etc. In chords such as [G2c2], only the highest note is considered. Any warnings or error messages from the ABC parser are suppressed unless the -c option is given.

OPTIONS

-a

Report any matching bars. By default, if the template file contains a sequence of several bars, the program will try to find places in the data file where the whole sequence matches. With this option, it returns all places in the data file where any of the bars in the template file match.

-br d

`Brief mode' is designed to identify groups of tunes sharing common bars. In this mode, the program determines the number of all bars in each tune from the data file which are also present in the template file. If the number of common bars is greater than or equal to the value of the d parameter, the program reports the tune and the number of common bars. Currently there is no user control of the matching criterion; the rhythm must match exactly, and the notes are transposed to suit the key signature.

-c

Display error and warning messages from the ABC parser (which are suppressed by default).

-con

Do a pitch contour match. In this case, the program uses the key signature only to indicate accidentals. The pitch contour is computed from the pitch difference (interval) between adjacent notes. That is, C2 DE, c2 de, and G2 AB all have the same pitch contour.

-ign

Ignore simple bars.

-length_hist

This does no matching at all but returns a histogram of the distribution of note lengths in the data file. The output looks like

length histogram
12 100
24 20
36 6
48 2
72 4

where a quarter note is 24 units, an eight note 12 units, a dotted half note 72 units etc.

-pitch_hist

This does no matching at all but returns a histogram of the distribution of pitches in the data file. The output looks like

pitch histogram
64 2
66 9
67 11

where the first number on each line is a MIDI note number and the second is a count of the number of times that note occurred.

-qnt

Do a quantized pitch contour match. This works as described above for the -con option, but will also quantize the intervals as follows: Unison and semitone intervals are assigned value 0, major 2nds to major 3rds value 1, and a perfect 4th or greater value 2. Negative numbers are used for descending intervals.

-r n

Resolution for matching. If the n parameter is zero, a perfect match must be found, meaning that the lengths of each note in a bar must match exactly in order to be reported. The larger the value of n, the looser the match will be. Note lengths are converted into temporal units where a quarter note is normally assigned a value of 24 (therefore an eighth note has a value of 12, a sixteenth a value of 6, a half note a value of 48 etc.) If you specify a temporal resolution of 12, then the pitch values of the notes only need to match at the time units that are multiples of an eight note. This means that the program would match the two bars C2 D2 and C C D D, as well as C2 D2 and C/D/C/D/D2. By selecting a suitable value for n, you can search for matches only at the beginning of a measure or at the beginning of each beat.

-v

Run verbosely.

-ver

Display the program's version number.

LIMITATIONS

The program has some limitations. For example, the data file must contain bar lines, and tied notes cannot be longer than the equivalent of 8 quarter notes. A resolution (-r option) that is too small may cause some buffers to be exceeded. When there are differences of key signatures of more than 5 semitones, the program may transpose the notes in the wrong direction. Also, tunes with more than one key signature or time signature may not be processed correctly.

SEE ALSO

abc2midi(1), midi2abc(1), mftext(1)

AUTHOR

This manual page was written by Anselm Lingnau <lingnau@debian.org> for the GNU/Linux system.

VERSION

This manual page describes abcmatch version 1.42 as of 21 December 2006.