Scala scale file format
This page is intended for developers of music software who wish to support reading or
writing of Scala scale (.scl) files. This file format for musical tunings is a standard
for exchange of scales, owing to the size of the scale archive of
over 4000 scales and the popularity of the
Scala program. With the
file's human readable format it's also useable for including scales in e-mail or
discussion group postings.
So these lines are all valid pitch lines:
- The files are human readable ASCII or 8-bit character text-files.
- The file type is .scl .
- There is one scale per file.
- Lines beginning with an exclamation mark are regarded as comments and are to be ignored.
- The first (non comment) line contains a short description of the scale,
but long lines are possible and should not give a read error. The description is
only one line. If there is no description, there should be an empty line.
- The second line contains the number of notes. This number indicates the
number of lines with pitch values that follow. In principle there is no upper
limit to this, but it is allowed to reject files exceeding a certain size.
The lower limit is 0, which is possible since degree 0 of 1/1 is implicit.
Spaces before or after the number are allowed.
- After that come the pitch values, each on a separate line, either as a
ratio or as a value in cents. If the value contains a period, it is a cents
value, otherwise a ratio. Ratios are written with a slash, and only one.
Integer values with no period or slash should be regarded as such, for example
"2" should be taken as "2/1". Numerators and denominators should be supported to
at least 231-1 = 2147483647. Anything after a valid pitch value should be
ignored. Space or horizontal tab characters are allowed and should be ignored.
Negative ratios are meaningless and should give a read error. For a description of cents,
- The first note of 1/1 or 0.0 cents is implicit and not in the files.
- Files for which Scala gives Error in file format are incorrectly
formatted. They should give a read error and be rejected.
Here is an example of a valid file:
A simple advise: put the filename on the first line behind an exclamation mark. Then someone
receiving the file and reading it knows a name under which to save it.
1/4-comma meantone scale. Pietro Aaron's temperament (1523)
To developers of MIDI software: you should be aware that there is another Scala file
type for mapping key/note numbers to scale degrees, called a keyboard
mapping, with file extension .kbm . In absence of support for keyboard
mapping files, you may choose any mapping you want, but it will severely limit
the musical usability, as argued in this article from SoundBytes.
The description is here: Scala Keyboard Mappings.
1) The user can choose the character set that he/she requires, but
if a file is intended to become included in the scale archive, it should be in
ISO 8859-1 'Latin-1' or the ASCII subset.
The scale archive can be freely downloaded. See the contents
listing for a brief description of each scale file. The scales are at:
Other programs which support the Scala scale format:
© Manuel Op de Coul, 2001-2018
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