Melissa Weber is marveling at the architectural details and acoustics-conscious stage set-up at the Little Gem Saloon’s Ramp Room on the historic 400 block of North Rampart Street. As is often the case here, the stage is dark, the room is empty and the sounds of tipsy tourists emanate from downstairs. Weber hopes to change that.

On September 12, vibraphonist Warren Wolf kicks off Weber’s Gem Sessions, a monthly modern-jazz series presenting some of the genr...