At your beck and call
* Eddie DeLange wrote this old jazz standard in 1938. With his band he introduced and featured a new song, “At Your Beck and Call”, a collaboration with Buck Ram, a young tunesmith who would one day find his own fame as manager of the 50s rock and roll vocal group, The Platters. Mildred Bailey sung this one in 1938 and several others after then.
** at (someone’s) beck and call: subject to (someone’s) slightest whim (short for beckon)
(Collins Concise Dictionary, 1998, p.112)