Bringing an instrument is generally fine. A violin, a guitar or something similar works here, as long as sleep and meeting times are respected.
The main building has extra sound-insulating layers between the rooms, though some sound still carries through doors and hallways. Outside the usual working and quiet hours it is rarely an issue. What matters most is coordinating with the up to two rooms next to yours.
Two spots work particularly well, because only a single room borders each of them:
The sunbathing terrace on the top level - the only adjacent room is Acro Atrium
The living room - the only adjacent room is Beach Base
The common areas are large enough to find a flexible solution when needed.
There is no permission to ask for and no fixed practice schedule. Two things are worth doing before you start:
Ask the person living in the room next to yours - they are the one who actually hears it
Post it in the coliving chat, so anyone else who would be affected can say so
In practice that settles it. People here are used to arranging things this way, and the answer is almost always yes. Beyond that, the usual quiet hours from the house rules apply.