A flexible music instrument case uses an interchangeable lid system to allow different types of lids to be attached to a main body depending on the particular needs of the user. The main body of the music case has an internal chamber configured to closely contain and protect the musical instrument or instruments, depending on the particular instruments being carried. The main body is somewhat structured to maintain a container shape, and may include various levels of rigidity. In addition, the main body further has at least one attachment mechanism attached to a portion thereof, to allow an interchangeable lid to be removably attached to the main body. The interchangeable lid has a similar attachment mechanism attached thereto to allow for the removable attachment of various lid elements. The interchangeable lids are configured differently to allow a user to configure the carrying case as necessary, and may include accessory compartments, sheet music pockets, or extended accommodations to allow portions of the musical instruments to extend beyond the open top while also being contained. Additional handles, wheels and straps are also included to increase the ease of use for the musical instrument case.