MAINSTEM - Free Jazz Leadsheet

“Mainstem” is the title of a composition associated with the swing era, though without specifying composer or first recording details, it is challenging to confirm which version is intended. It may refer to a big-band instrumental or a classic dance‑band tune.

If you provide further information — such as the composer, year, or a well-known artist associated with it — I can offer a detailed historical and musical description.