What was that Dr Who in Tom Baker where the Dr and IIRC Romana (maybe Leela) were tied up with vines which would shrink as they drived and stretch them (people not the vines)?
The Dr sang out a high note (which caused Romana/whoever to tell him off as it didn't hurt that much so soon). However what he did was cause a glass skylight to break letting in rain onto the vines which then went soggy and slack.