The Track Check option can be interesting and helpful in two ways.
Firstly, this service offers the possibility to have a title checked thoroughly before the actual mastering to get the best possible results during the mastering.
The client receives professional feedback including tips and suggestions for improvement.
This also includes the evaluation of whether a stereo mastering is sufficient or if a stem mastering is recommended.
Thus, Track Check is a preliminary test to determine whether a title meets the requirements for a good mastering result.
Secondly, this option is also suitable for producers who do not want to order a mastering yet but want to know more about the sound and quality of their production. We can also discuss the musical/creative side of a production or the arrangement if required.
Further information can be found here
(Only pay if you like the master)