I understand how to create "normal" tuplets in ABC: for example, where a triplet contains three notes, or a quintuplet contains five notes.
X:1
T:"Normal" Tuplets
M:2/4
L:1/16
K:none
(3A2A2A2 (5AAAAA
But I can't figure out how to do it if I want, say, a triplet with a quarter-note and an eighth note. Can ABC do that? How should it be coded?
This is explained in the tuplets section of the ABC standard.
To code tuplets with multiple note-lengths, use the p:q:r notation.
More general tuplets can be specified using the syntax (p:q:r which means 'put p notes into the time of q for the next r notes'.
To render a triplet comprising a quarter-note (crotchet) and an eighth-note (quaver), you would write (3:2:2. [Note the use of the abbreviation (3::2 in the third triplet.]
This code...
X:1 T:Tuplets Example M:3/4 L:1/8 K:none (3:2:2 A2A (3:2:2 A2A (3::2 A2A
...renders this result...
X:1
T:Tuplets Example
M:3/4
L:1/8
K:none
(3:2:2 A2A (3:2:2 A2A (3::2 A2A