Tuplets may include embedded tuplets

[newlandsvalley]

see for example the penultimate bar in http://abcnotation.com/tunePage?a=www.folkwiki.se/pub/cache/_J%F6ns_Lars_fars_Bodapolska_c32f9a/0001.

[newlandsvalley]

It's unclear to me whether we want to do this. There seems to be no mention of the possibility in the spec and I've seen only this one example of it in the wild.

[newlandsvalley]

another example is this one.

[newlandsvalley]

Apparently, abcMIDI and the Abc/MusicXML translators do not support nested tuplets.