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 concert posters, record album covers and tee shirt graphics.
It is now available digitally as Nouveau Artiste JNL.
As a side note, a 1940s reprint of the sheet music was done in a popular metal typeface, which was also redrawn digitally and available as Elite Resort JNL [in both regular and oblique versions].
Font Family: Nouveau Artiste JNL
Tags: 1900s, 1960s, art nouveau, bold, casual, decorative, display, headline, novelty, retro, sans serif, vintage