Easton's Bible Dictionary (1897)
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.
Smith's Bible Dictionary (1863)
(lilies). “To the chief musician upon Shoshannim” is a musical direction to the leader of the temple choir which occurs in (Psalms 45:1; 69:1) and most probably indicates the melody “after” or “in the manner of” (Authorized Version upon”) which the psalms were to be sung. Shoshannim-eduth occurs in the same way in the title of (Psalms 80:1) ... As the words now stand they signify “lilies, a testimony,” and the two are separated by a large distinctive accent.
In themselves they have no meaning in the present text, and must therefore be regarded as probably a fragment of the beginning of an older psalm with which the choir were familiar.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
SHOSHAN'NIM (lily), Ps 45; Ps 69, title, HOSHAN'NIM - E'DUTH (lily, a testimony), Ps 80, title, probably signifies the melody to which the Psalm was sung. Some have regarded it as the title of a bridal-song, while others think it means a musical instrument.
Hitchcock's Bible Names (1869)
those that shall be changed