I think I have never bothered to learn them because whenever I see it, I know it's only there because the hand with which I am supposed to play that bit is not the hand that staff is written for. Maybe it's not always so clear. I am thinking I have mostly seen it in Beethoven? I really don't remember. Bad side-effect of memorizing quickly: I don't remember scores.

Well it depends on what you play, but starting with Liszt it becomes relatively frequent ; Rachmaninov has quite a lot of it (though I wish it was indicated with greater frequency, sometimes I just can't figure out if you're supposed to use the pedal or cross your arms in a weird way), Prokofiev too.

I've been learning the first Medtner sonata, and while you don't have m.d. (though it does often appear in Medtner too), there often are "brackets" ( [ ) linking some notes to indicate they should be played by the other staff's hand - though it's often quite obvious.

Well, I take it that m.d stands for "main droite" (right hand in French) and m.g for "main gauche" (left hand), doesn't it ?

Yes, congratulations for your french !

To Monica:
- m.d. = main droite. Droite has the same root as right (according to my English teacher, but this is a 40 year-old memory...). As a matter of fact, the phonetic of the two words resemble, and there are two important letters in common (r and t);
- m.g. = main gauche. Gauche does not sound as left nor as right...

Hope this helps. However, the post-it issue, while not very esthetical, is also a good approach !

Henri, Teddy, and Francois - thanks for your tips.

Teddy and Francois - your ideas about the letters i, r, and t make sense to me. If after all this I still cannot remember m.d. and m.g. then I may have to resort to the post-it notes (not going to look very good in my nice living room, though - I better just remember!).

Bonjour, since the etymology of English words are 80% French anyway....

The definitions of droite and gauche stem from social behavior over the ages. As is the convention, we shake hands with our right hand and not with our left. Shaking hands with your left hand would be gauche or awkward, as has become the English connotation over time.

Therefore:
m.d. = diplomatic == RIGHT
m.g. = gauche or awkward == LEFT

Ok, that's another good one. Thanks, George! Surely I should remember m.d. and m.g. now - will find out tomorrow when I sit down at my piano....

Aucun mérite, puisque je suis 100% français (mais je n'étais pas sûr de l'origine étymologique de ces abréviations ) !