How to change the intrument?

it sounds guitar or piano by default, but can i change to sound a flute, what do i do

You can change the instrument in Hookpad projects by going into the “Mix” settings. Note that in order to save changes to your mix you need to be a Plus member.


and can i change the instrument at any point in the music

There can only one instrument per part per tab. So you can’t have both a guitar and a piano as the melody, for example.

I may not have phrased my question correctly, Yes, i do understand that only one instrument can be related to any one part at any one time, but can i change that one instrument related to voice 1, for instance , to another instrument, at any point while the music plays

No. You can’t. Unless the devs make it a feature, you can’t have parts changing instruments mid-song.