There’s a bug that got introduced which causes the octave switch to take effect 100ms later than it is supposed to in the audio script.
Musical instruments haven't been playing correctly as this bug has been re-introduced in the 26. November patch
i Ask Anet to please address this problem for the sake of all Music Guilds that rely on Anets code working properly as soon as possible .
if your experiencing this bug feel free to share your experience with this bug in the comments below .
here is some info about this bug ( this is not the first time its happened )
todays reddit forums about the bug
please share your experiences if could help Anet get this problem done . thank you for your time .