Lilies, the name of some musical instrument, probably like a lily in shape (Ps. 45; 69, title). Some think that an instrument of six strings is meant.
those that shall be changed ...
Hitchcock's Bible Names Dictionary
(lilies). "To the chief musician upon Shoshannim" is a musical direction to the leader of the temple...
William Smith's Bible Dictionary
In title of Ps. 80 (R.V. marg., "lilies, a testimony"), probably the name of the melody to which the...
Easton's Bible Dictionary