I’ll try to sketch the problems than would occur. Suppose you have an event like this, when played, expansion works according to the current convention, 4 synths with instrument \a, freqs 100 to 400 and pannings -1, 0, 1, -1.
// (0)
(
\instrument, \a,
\freq, [100, 200, 300, 400],
\pan, [-1, 0, 1]
)
Now, what should be done with this ?
(
\instrument, [\a, \b],
\freq, [100, 200, 300, 400],
\pan, [-1, 0, 1]
)
(A) According to the current convention we could produce 4 synths with frequencies 100 to 400 and instruments \a, \b, \a, \b.
(B) On the other hand one might think, no, with this writing I want the expansion of type (0), but on two instruments.
Both thoughts are legitimate, but which one should be preferred ? Ok, we could decide for two types, say ‘noteX1’ and ‘noteX2’ but next, if we invent the opportunity to have multiple instruments we would also want to differentiate the inputs for both instruments, which could again be numbers or arrays. This forces to cope with the handling of unpleasant nested lists and their possible ambiguities, the option of array arguments in either instrument makes it yet worse! All in all this looks like a nightmare to implement and I’m not surprised that nobody wants to touch it …