Clamped Tongue And Tits
Tightened properly, those screw clamps on her nipples will be making her want to scream. But the clamp on her tongue should be limiting her ability to get all that loud with it:
From a vintage bondage magazine, but I don’t know which one.
Elsewhere on Bondage Blog:
Or one could gag her with a harmonica. It’s not much by way of melody, but the rhythm of airflow in and out gives a guy some idea how she’s coming along.