Two options. Give them away now to the person or organisation who you know can make good use of them on condition that you retain their use for life and put it all in writing.   Or, if you want to raise cash for your dependents and the instruments are of recognised quality, do a little research and find a good auction house which specialises in instruments (eg Phillips in UK), and leave clear instructions so that your beneficiaries know how to set up disposal sensibly. Same with books which can sold through appropriate specialist journals as a library.