 Vocal tremor VT is a form of benign essential tremor. In less severely affected persons, vocal tremor is action-induced and occurs during vocalization only. In more severe cases, the tremor can be present also during exhalation and whispering and affect other structures, such as the velum and pharynx. This is also considered a neurological disorder but may differ in character from SD. Both these disorders can co-occur with SD but can also occur independently. 