Lyre
By the time Orpheus met Eurydice, his lyre was essentially a part of him, never leaving his side for long. It had been a gift from Hermes, who owned it originally, and told tall tales of inventing the instrument. Whether it was true or just a bit of added flair, Orpheus didn't know.
Before it was properly his, Hermes had given permission to try it out, and he found that whether he played existing music or original tunes, the bar patrons always asked for more. Sometimes he'd spend hours staying up late to tune the instrument and practice, and Orpheus counted himself lucky Hermes was a patient sort.
And from the moment Orpheus was old enough to hold it correctly, to play it well, he knew he'd carry it for the rest of his life. The lyre carried his joys, dreams, and sorrows to the winds, music saying what words alone could not.
And when Orpheus played, strumming and singing his songs to the world, the world sang back.