I'm on Fran's thought - use or lose. I stand when playing (for the last 10 years or so). I drive quite a bit to jobs, etc and sitting in a car is enough - I limp to the front door and fit in well with the residents smile But standing up and moving around gets the circulation going again. Plus I sing much better (need all the help I can get).
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Live: Korg PA4X/Bose L1 Pro 8/Senn 935

Studio: Korg PA4X/Kawai MP7SE/Tascam DP24SD/Sony C80/AGK 214/ATEM Mini Pro switcher/