Definition of "tunelessly"

He whistled tunelessly his one air, beating his own time with a stick on the toe of his blucher[.]

1902, Barbara Baynton, edited by Sally Krimmer and Alan Lawson, Bush Studies (Portable Australian Authors: Barbara Baynton), St Lucia: University of Queensland Press, published 1980, page 13

After a pause that he spent whistling tunelessly under his breath, he said: “Hello, Miss Henry? […] ”

1931, Dashiell Hammett, chapter 8, in The Glass Key‎, New York: Vintage, published 1972, page 159

Night descends moonlessly / Cops are humming tunelessly / Walking in a straight line / Cold pistol in the inner coat pocket

2007, “Life After Sundown”, performed by Glass Candy