Scala (tuning format)

Manuel Op de Coul wrote the Scala program at the Huygens-Fokker Foundation in the Netherlands, and its archive holds several thousand tunings, from ancient Greek tetrachords to gamelan and modern experiments. The file format has outlived the program in importance. An .scl file is plain text: comments start with !, followed by a description, the number of notes and one line per note. A value with a decimal point is read as cents, a fraction like 3/2 as a frequency ratio.

The last line gives the period, usually the octave. A separate .kbm file says which key plays which scale degree. Surge XT, most soft synths with microtonal support and MTS-ESP all read it, which makes it the closest thing to a standard the tuning world has outside MIDI.