Possible Clues:

• Talked indistinctly in a low voice
• Talked under one's breath
• Spoke indistinctly in a low voice
• Talked in a barely audible voice
• Spoke in low unclear voice
• Spoke in low unclear tone
• But Lo! By the sound of it, thus spake a thousand
• To have said anything so low would have turned your stomach and tree'd you
• Murmured, mumbled
• It's grand to have said anything so low as this