undertone

Did he and his master converse? Watt had never heard them do so, as he surely would have done, if they had done so. In an undertone perhaps. Yes, perhaps they conversed in undertones, the master and the servant, in two undertones, the master's undertone, the servant's undertone.

Sedentary occupations are likely to result in undertone, and this undertone not being relieved by physiological means, constipation is a probable outcome.