The Business and Enterprise subscription plan options both cover multiple end clients (brands), as long as the client's employee count is under the threshold of what your subscription plan covers. For example, if you have a Business subscription plan for ‘Up to 50’ employees, it would not legally cover a brand with 100 employees.
If you would like to purchase a single song license for a project that isn't covered under the scope of your subscription plan, you are welcome to do so by selecting the shopping cart icon on any song page to open the single-song license builder.