The bell is the only musical instrument traditionally used in Wicca. Ringing the bell is thought to either summon or dismiss spirits at the opening and closing of the ritual circle.
Some people will use music as part of their rituals, particularly for help in grounding and meditation, but this is a personal preference and not specifically Wiccan at all.
They are sometimes used in rituals, that is true. But they are not part of traditional Wiccan practice.