I heard about an ancient Japanese musical instrument by this name that could also be used as a club for self-defense. Then I began to think of what this might look like in Vana'diel. Here is what I came up with.

(Club) All Races
DMG:85 Delay:267
Cannot equip instruments
Shakuhachi no Sensei
All songs+3
Singing skill+15

"Shakuhachi no Sensei" is an effect similar to the "Iridescence" effect on the iridal and chatoyant staves. It raises the bard's club skill rating to C+ and wind instrument skill rating to B+ while equipped, and it also doubles as your instrument (hence the "Cannot equip instruments" effect on it). When playing a song, there would be a unique animation in which the bard lifts his weapon to his/her lips and plays it, rather than pulling an instrument out from the waist area to play and putting it back. I was careful to make a dagger/Gjallarhorn combination better than this while still making the shakuhachi more than useful.