minstrel: 12/8 time signature

[warden]

Greetings to the list!

I have a question regarding time signatures in music.

I was listening to some Scot Joplin rag time a while ago while looking 
at the sheet music and noticed that the syncopation is written as 
triplets, in other words, a quarter note and an eighth note combined as 
a triplet for one beat.

Recently I heard a medieval song called "Da Que Deus Mamou" by Alfonso 
X, which has the same syncopated rhythm (although slower).  It was 
written in 12/8 time with alternating quarter notes and eighth notes for 
the fast part and dotted quarter notes for the slow part.  If I tap my 
foot really fast, I can do 12 beats to the measure, but I realized that 
rhythm is actually 4 triplets per measure. The natural foot tapping mode 
is 4 beats per measure with the dotted quarter note getting one beat.

So my question, is how best to describe this.  There doesn't seem to be 
a convention for this type of time signature except to write it as 12/8, 
which doesn't reflect one beat for the dotted quarter note.  The 
alternative is to write it out as triplets so that the quarter note gets 
one beat.

Any thoughts or comments appreciated!

-Robert
Caer Galen
(Boulder, CO)