From the PMI perspective, change control process is mastered by configuration management. We define the configured items (CIs) upfront during planning phase such that if a change occurs to any of predefined CIs, change process is triggered. CIs can be any hardware, software ,people, documents or any entities that may impact or be impacted by the project progress. Also,The analysis of stakeholder power/interest/influence can be a factor here to determine wether or not change process is required.
Practically speaking, however, processes can always be tailored to organization needs and to its best interest. As Elizabeth indicated, it could work by just updating the registerer without the need of a formal approval. Enlarging CIs in our project can sometimes be recognized as a waste if the need is not assessed properly.