My 12 year old son wants to play Canon by Pachebel (rock version) for a talent show in 3 months. How hard is that to learn? He has 2-3 years experience.

I'm wondering if I should steer him away to something else.
I reckon he'd be likely to struggle at the sweeping parts and the shredding. He'd probably be ok with the powerchords and main riff though. In any case though I'd reccommend you steer him to something else.
ye i'd say something else too, there's some really tricky bits!
you could let him try for a month and a half and if he's not gonna pull it off, he'll have time to learn an easier song
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if he practices it hard enough, then ya, let him improvise over an easy pentatonic scale instead of shreding