I have not yet found anything on your (a) case, but have some information about your (b) case. It appears that there is not consensus on how these polyrhythms should be played. Is this accurate? How do most performers of Bach play such rhythms? Most of the pieces I'm interested in are fast so I can't really tell when listening to Gould or Hantai. If true, this would make playing the piece I'm having trouble with (Goldberg Variation #29) much easier, but I was surprised. ('zapis' and 'wykonanie' mean 'notation' and 'execution', respectively)Д«) When threes are combined with twos consisting of a dotted note and a supplementary value - the supplementary value is played together with the third note of the three, e.g:ДЄs you can see, quotes from Bach are used to illustrate the point. Here are several examples:ДЄ) When threes are combined with twos, the first note of the two is prolonged so that the second one is played together with the last note of the three, e.g: (.) It is prudent to note that even until the latter half of the 18th century, combinations of superimposed threes and twos were not employed. I was reading up on tuplets and polyrhythms because I was having trouble playing some of Bach's keyboard works containing three-against-two rhythms.

4 note version of a triplet