> I don't get the musical meaning of having two simultaneous trills > *in the same voice* (as opposed to simultaneous trills in two > different voices).
Irrespective of the current issue, having a trill on a chord, with all
notes involved, is happening regularly in piano music. Attached is an
example from Fauré op. 19 – this old edition uses accidentals above
the trill, but a modern one could theoretically use secondary notes
instead.
Werner
