Thank you, Glen and Nigel.
It's really weird and at the same time interesting to see how the lack of physical energy affects a thing like playing music, that is not tiring in itself (at least at the body level), but requires indeed a lot of mental concentration.
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Korg Kronos 61 and PA3X-Pro76, Roland G-70, BK7-m and Integra 7, Casio PX-5S, Fender Stratocaster with Fralin pickups, Fender Stratocaster with Kinman pickups, vintage Gibson SG standard.