For muted audio I think a muted speaker icon on a button displayed in clicked/active state would be the most intuitive version. Aside from that roughly 100% of

For muted audio I think a muted speaker icon on a button displayed in clicked/active state would be the most intuitive version. Aside from that roughly 100% of applications I've been using use the "show current state" approach in this specific case. I don't think I've seen a media player which does it differently.