8 octaves above middle c is aprox 64000Hz so inaudible (unless you're a bat) the highest audible note will be about an octave and a 5th below that (aprox 20kHz), and then only if you've got good hearing.
As for the highest playable note, you can get the e 4 octaves above middle c using harmonics on a violin, i don't think you'll get much higher than that, although i think some organ stops have pipes that play a 19th or 22nd (3 ocataves) above so that would put them a just a bit higher (aprox 8kHz)
Extremes of musical notation
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