Instruments with the coda trait work mostly like staves and have the staff trait. There are two differences: Coda instruments are in the form of musical instruments, and they can be prepared only by bards. Because they're not physically staves, you can't attack with a coda instrument, nor can you etch it with weapon runes. The process of preparing a coda instrument involves playing significant portions of songs related to the spells within the instrument—either old standards or ones of your own creation. This leaves magical reverberations within the instrument that allow you to complete the songs by playing their coda later in the day.