When you create a new Ensemble or Class or Group Lesson in the Ensemble Codes file, the Pay Category is copied across from the staff member's record in the Contacts file. If the teacher is a Sessional teacher, then 'Sessional' will copy across. 'Sessional' records are imported into the Salaries files to calculate payments. Occasionally you may have a staff member who is SALARIED, but they take a couple of ensembles or classes over and above their 'load', so they need to be paid for these sessions as if they were a SESSIONAL member of staff. You can change the Pay Category of individual records in the Ensemble Codes file.
As staff members loads change from year to year (and sometimes term to term), you will probably want to RESET ALL Ensemble records at the end of the year - back to the default Pay Category as determined by Employment Type in the Contacts file.
Click this script to reset ALL Ensemble records in one step. Be careful, though. This step can't be undone. Don't do it until the pays have been finalised for the year. And if you are a multi-campus school, be warned that this script is performed with FULL ACCESS PRIVILEGES, so it will reset ALL records for all campuses. (Perhaps check that everyone is ready before you do it!)