Guitarist and songwriter Whitney Smith may be best known as the leader of the Big Steam Band, but he’s also an adept vocal coach. He recently launched the Jazz Cab, a Friday night series in which he and bassist Jordan O’Connor accompany cabaret singers who draw from the oeuvres of composers past. This time around, the artists each present a set of songs by Johnny Mercer and a set by another composer. Mercer was one of the great lyricists, occasionally writing music as well (“I’m an Old Cowhand”) but usually teaming with others to create such masterpieces as “Too Marvelous for Words” and “Come Rain or Come Shine.” Kinga performs Irving Berlin, May 2; Jen Sagar tries out Jimmy Van Heusen, May 9; Kristen Rundle takes on Jerome Kern, May 16; Elizabeth Bettencourt tackles Leonard Cohen, May 23; and Vincent Wolfe does Gershwin, May 30.—Brent Ledger