Double Bassist Carter Callison likes to work with different tunings on the double bass. He has developed a Double Bass Retuning Pedal, which allows him to change the tuning of his bass while he plays:

Double Bass Retuning Pedals (a.k.a. “Scordatura Pedals”) have gone from being a simple DIY project in my garage to becoming a key element in my PhD research. After my original handmade prototype showed potential, I began the tedious process of developing CAD drawings with a design company in South Carolina in order to transform my basic idea into a nuanced product that can handle vigorous professional use. Now that the CAD drawings are done, I am at a critical stage where a lack of funds has put a hold on what I believe is an important project for the development of the double bass. The funds that I am requesting will allow for the manufacture of a professional quality prototype which will allow me to continue my research at the Royal Academy of Music.