His father was a former magician who had made his fortune from Hamlin's Wizard Oil, a patent medicine sold as a cure-all under the slogan "There is no sore it will not heal, no pain it will not subdue."

His friend Victor Herbert had written the leading tenor role (Lt. Paul Merrill) in his new opera Natoma for Hamlin's voice.

One of the Philadelphia critics wrote of his February 1912 performance there: Mr. Hamlin's voice has much to commend it in the way of smoothness and sympathy, and he sings with taste and skill, while he also carried himself well, put real feeling into his acting, and altogether made a highly favorable impression.

These included Pinkerton in Madame Butterfly, Gennaro in Jewels of the Madonna, Edward Plummer in Goldmark's Das Heimchen am Herd (performed in English as The Cricket on the Hearth), Don José in Carmen, Cavaradossi in Tosca, Florindo in Parelli's I dispettosi amanti, François in Madeleine, and Walter in Bucharoff's The Lover's Knot at its world premiere in 1916.

In late October 1922 Frank Damrosch announced that Hamlin would be joining the faculty at the New York Institute of Musical Art in the coming year.

She performed in recitals and sang minor soprano roles with Chicago Civic Opera and later was a voice teacher at Smith College from 1939 to 1959.