The tablature numbering normally produced by Sibelius consists of fret numbers on the 12-tone chromatic scale, for use with instruments having chromatic frets, such as the guitar.
Certain instruments, such as the Mountain Dulcimer (also known as Appalachian Dulcimer), have a fretboard with frets arranged on a diatonic scale: in the case of the traditional Mountain Dulcimer the scale is Mixolydian. Users of such instruments prefer tablature displaying the diatonic step number, rather than the chromatic one.
The DiatonicTab fonts are a set of small fonts (supporting only digits), which use OpenType features to convert a chromatic step number to a diatonic step number. When used as the font for Sibelius Text Style Tablature numbers, they cause diatonic step numbers to be displayed on the TAB staff. Chromatic note pitches intermediate to the basic diatonic steps will be indicated by the diatonic step number below with a + symbol, and if quarter-tone notes are present in the TAB staff, they will appear with ¼ or ¾ symbols. The score itself remains unchanged (apart from the font selection for tablature numbers): only its external visual rendering changes when viewed or printed.
If the Sibelius score file (or an SVG graphic exported from it) is transferred to another computer, then the relevant DiatonicTab font must be transferred with it and installed on the destination computer. This is not required when transferring exported PDFs to other computers.
Fonts are provided for all seven modes of the diatonic scale: Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian, and Locrian. For the Mountain Dulcimer, the Mixolydian font (DiatonicTabMix) should be used.
Please consult the included documentation for further instructions and known limitations.