This unrestricted style of lettering was popularly embraced and revived by the hippie counterculture of the mid-1960s through the mid-1970s through their rock performance posters, record album covers and tee shirt graphics.
It is now readily available digitally as Nouveau Artiste JNL.
As a side note, a 1940s reprint of the sheet music was performed in a popular metal typeface, which was likewise redrawn digitally and readily available as Elite Resort JNL [in both routine and oblique versions]
Font Family: Nouveau Artiste JNL
Tags: 1900s, 1960s, art nouveau, bold, casual, decorative, display, headline, novelty, retro, sans serif, vintage