How to implement a many-to-many relationship

Many-to-many relationship is implemented on Demo application with the Invoices table. Each Customer can have multiple Tracks purchased, and each Track can be sold to multiple Customers. No code is needed to achieve this.

What Jam.py is providing is even more. As seen on Tracks form, it is possible to identify which Customer purchased which Track, with automated summary. Some code is needed to achieve finding the Customers.