As Gershwin's career began to open out, he continued to study with, among others, Edward Kilenyi, a well-respected private teacher who imparted the rudiments of harmony and orchestration. About this time, one of the "tunes" was worked into a piano piece, and it was as an exercise for Kilenyi, around 1919, that Gershwin scored it for string quartet as his Lullaby. Private copies soon circulated among friends and it was often performed at musical gatherings, to the young Gershwin's great satisfaction. After a "tuning up" gesture, the slowly swinging blues melody is strutted in a skillfully varied exposition leading to a plaintively muted, hesitant moment which gives way to a rush of the warmest, most caressing lyricism before the initial blues returns to fade exquisitely. - AllMusic.com