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2021.05.24

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Seymour Shlien
2021-05-24 13:57:28 -04:00
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doc/abcguide.txt
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@@ -1,10 +1,11 @@
Guide to writing abc for abc2midi
---------------------------------
Guide to writing abc for abc2midi - minor revision [JA] 2021-05-24
--------------------------------------------------------------
Updated June 1 2017. %%MIDI program ranges from 0 to 127 not 1 to 128.
The defining document for abc is the abc version 1.6 specification which can
be found at http://www.gre.ac.uk/~c.walshaw/abc2mtex/abc.txt . This document
is a description of abc as interpreted by abc2midi.
The abc notation language is described by the version 1.6 specification
document and later modifications to this document referred to as
version 2.1 and version 2.2. These can be found at abcnotation.com .
An abc tune consists of a header followed by a body. Each line in the
header is a different field starting with a letter immediately followed
@@ -160,15 +161,43 @@ K:G clef=soprano octave=-1 transpose=-1
The clef is recognized by typesetting programs such as yaps and abc2mps
and in some situations it will cause abc2midi to transpose the notes
up or down by an octave. Recognized clefs are treble,
bass, baritone, tenor, alto, mezzo and soprano. There are also variants
of these clefs; treble-8, tenor-8, treble+8 covering ranges which are an
octave below and an octave above the normal treble clef. Other
variants are not recognized at this time. No transposition is
assumed for the bass clef since many abc files enter the notes
with all the commas.
bass, baritone, tenor, alto, mezzo and soprano.
The octave specifier is a convenience to make entering music easier.
It allows the user to avoid repeatedly entering commas or apostrophes
Clefs with +8, -8:
Sometimes, you will find written music where there is a treble clef (or
some other clef) with a small 8. The meaning is that every note is to
be played an octave higher than shown. Suppose you notate the abc note A
using a treble clef. This appears as a note between the second and third
lines from the bottom of the stave. Then with a treble+8 clef (which looks
exactly the same except that it has a small 8), a note at the same position
on the stave lines is now played as abc note a (which is normally put on
a line one line up from the top line of the stave). Similarly, the
treble-8 clef indicates that every note is to be played an octave lower
than shown, so note A would be played as A, .
The abc standard versions 2.1 and 2.2 support this idea, but the way
the abc notation is interpreted changes when you have clef=treble+8.
With clef=treble+8, every stave position is interpreted as being an
octave higher than if you had clef=treble e.g. the note that sounds as
a does in normal abc is written as A in abc with clef=treble+8.
The overall effect of this is that when you change a passage from
clef=treble to clef=treble+8, without editing any of the notes, every
note appears at exactly the same place on the stave lines as it did
before, but it is played an octave higher.
The benefit of this change in interpretation is that you can notate
very high or very low passages in abc without having to use lots of
' or , characters.
The octave specifier is a convenience to make entering music easier,
developed before the +8/-8 clef modifier and still supported. However,
to be compatible with other abc programs, it is recommended that you
use the clef modifier. The syntax
I:octave=<offset in octaves>
allows the user to avoid repeatedly entering commas or apostrophes
when entering a sequence of low or high notes. Both yaps and abc2midi
will transpose the notes by the specified number of octaves during
the parsing stage.
@@ -180,9 +209,10 @@ e.g. the passage B,,, C,, D,, E,, F,, could be written more compactly as
I:octave=0
Some instruments such as the Bb clarinet automatically transpose the
written music. For example in the case of the clarinet, the music is
written in the key of C but the instrument plays it in the key of Bb.
Some instruments such as the Bb clarinet are by classical convention
considered to transpose the written music. For example in the case of
the clarinet, the music is written in the key of C but the instrument
plays it in the key of Bb.
For multivoiced tunes, the %%MIDI transpose indication is not that useful
since it transposes all the voices by the specified amount. The
transpose=n subcommand in the K: field tells abc2midi to transpose