Although ModeWheel is a copyrighted application, it may be downloaded anonymously from this website and used entirely free of charge, subject only to the licensing terms detailed at the end of the QuickStart Manual posted on this website.
If you do find ModeWheel of value in learning more about these musical scales, please consider a small one-time anonymous donation via the Paypal link in the footer menu to help to support the cost of making ModeWheel available to everyone interested in music theory. However, just as Oliver Prehn says with respect to his own video lessons, please feel no obligation to do so.
More important to me is that you share the link to this website. As a life-long teacher, I’d like to reach as many music instructors and their students to promote a better understanding of scales and modes. (If you have your own website, an external link to my site may help even more.)
In either case, thank you for your interest in ModeWheel. I’ve worked to make this helpful both as a introduction for music students and as a convenient alternative for professional musicians to the online and print-based guides available on the internet.