tremulant
ˈtrɛmələnt
Definitions
1. adjective
liable to or causing trembling or shaking, especially of the voice
“The singer’s voice was tremulant and added a haunting quality to the song”
2. noun
a device, especially a tuning fork, used to produce a steady, low-pitched sound, used to stabilize the pitch of an organ pipe
“The organ’s tremulant added a rich depth to the music”