[MEI-L] comment on MEI @clef.trans values

[Craig Sapp]

Hello MEIers

In DTD 1.9b, I notice that there are
three choices for @clef.trans which is a
transposition value for a clef sign:

8va = transpose up one octave higher than written
8vb = transpose down one octave lower than written
15va = transpose up two octaves.

8va is the abbreviation for "ottava" in Italian.
8ba is the modern abbreviation for "ottava bassa"

15va does not exists as an abbreviation in Italian,
but is rather "15ma" which stands for quindicesima,
or a perfect 15th (two octaves).

It may be better to change "15va" to "15ma".  And if so,
then also add "15mb" represending "quindicesima bassa"
for playing two octaves lower for completeness.

Alternatively, the transposition could be given numerically
as in +1 for 8va, -1 for 8ba, +2 for 15ma and -2 for 15mb. Or,
semitones could be used: +12 for 8va, -12 for 8vb, +24 for
15ma, and -24 for 15mb.

-=+Craig