I am with and hear you re hearing loss ... haha ... pun!
I tend to double (or more) many instruments because I need to emulate the different registers in a different way. Basically the usual parameters we can automate don't always allow one to make those subtle, but important, changes to timbre. Of course we also need to articulate the instrument as it's played. Easier with a wind controller for a wind instrument versus a keyboard - etc...
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