Guitars are tuned an octave below where guitar music is written. I still laugh about the time I bought a guitar for my kids from someone who didn't know that and the high-E string mysteriously kept breaking. Clearly, I do not have 'perfect pitch'.
Fast forward to today when the Linux 'GNU Lingot' tuner app patiently explained to me, musically 'keen but subnormal', that my voice is an octave lower than I thought, for very obvious reasons. #SlowLearner but #EverythingIsRelative.

Still wondering why my little #Android hobby app is particularly successful in India and what happened in 2017. (Blue is overall number of devices running the app, red is India.) #EasyOpenLink #EverythingIsRelative