According to German case law is one thing accessory to another thing if the main proceedings, there is some physical connection and the accessories against the main thing has a serving function without the serving thing would already be part of. In Austria and Switzerland it is called appurtenances.
So accessories mean all items that are associated with a main product. Firstly, there may be articles that make the product an advanced feature like front carriers, carrier, carrying strap, Bandelieren etc. Secondly, it may be items to tune an instrument or product upgrade or enhance in any other way to get it sound to improve or make the product easier to use or while marching. But accessories are also needed to protect a valuable instrument to carry or from damage and dirt or to care for and maintain its functionality. A special form of accessories is "tool" as mallets and drum sticks to play a drum, a timpani or mallet instrument.
In any case accessory is not a mere accessory, but as important as the tools themselves!
We divide accessories into the categories "Lifting and carpets", "Covers & Cases" as covers, carrying case, flight case, storage pockets and fur cover, "Sticks & mallets" as drumsticks, drum sticks and mallets, stands, racks, holders, front feet, cymbal holders , note holder, leg straps, carrying plates, dampers, carrier, carrying scaffolding, portable racks, and Bandelieren strap and tuning key and skins.