Dorothy Smith wrote:

>Would someone (or several people) take a few minutes to answer a
>performance question that has been puzzling me? Are there straightforward
>rules about how to play a triplet rhythm in one voice against a dotted
>rhythm in another?

Depends on whom you want to take as an authority.  According to the book
Performance Practice, Music after 1600 (Norton), p.  134,

   Perhaps the most common clash of all is that between triplets and
   dotted figures.  Again, it is the post-Baroque treatises that are
   most explicit on the subject, but they disagree; C.P.E.  Bach and
   others assert that the second note of dotted figures occurring against
   triplets is to be played with the third note of the triplet, while
   Quantz and Agricola (the latter citing J.S.  Bach as his authority)
   insist that the dotted figure must be played in its true time value
   or overdotted, that is, with its short note coming after the last
   note of the triplet.  While this may be the right way to play some
   pieces, the great majority of scores...can hardly be played any other
   way than CP.E.  Bach's.  A brief _querelle_ on the subject occurred
   in 1959-60 in the pages of Die Musikforschung.  (Eta Harich-Schneider
   and Erwin Jacobi concerning dotted figures against triplets, in two
   articles, both entitled 'Ueber die Angleichung nachschlagender
   Sechzehntel an Triolen,' Mf, xii (1959) 35-59 and xiii (1960), 268-81.
   See also Jacobi, 'Neues zur Frage, "Punktierte Rhythmen gegen Triolen"
   und zur Transkriptionstechnik bei J.S.  Bach', Bach-Jahrbuch xlix
   (1962), 88-96.)

Casals, no HIP advocate himself, apparently played the dotted rhythms
against triplets with some over-dotting, thus exaggerating their effect.

Related rhythmic questions concern whether to play (for example) 32nd-|
dotted 16th-32nd 8th when 16th | dotted 16th 32nd 8th, as frequently occurs
in Handel; whether to play equal 8ths-against triplets so as to make the
2nd 8th coincide with the 3rd triplet 8th; and of course the French notes
ine'gales practice, which I believe is well-documented.

>I've read that in earlier music (through baroque) the two last notes
>of these figures should be played together.  However, one often finds in
>later music (for instance, Chopin's Polonaise-Fantaisie) that the score is
>clearly printed as if these notes are meant to be struck simultaneously.
>If so, why does the composer write the dotted rhythm?--why not just
>triplets in each voice?

I really don't know what to say about this, except that it's my
understanding that by Chopin's time rhythms were to be played as notated
(rubato being a separate issue of course).  The assumption is that a
compound meter would have been used had the composer wanted them to be
synchronized.

Chris Bonds