You're right, Maria, absolutely! I don't see any problem in the use of "easy" in the song lyric “Words don’t come easy.” You see, "easy" is working in that statement as an adverb in the sense of "without undue speed or excitement," as in "Take it easy" and "Promises come easy." It's tempting to use the adverb "easily" instead of the adverb "easy" when what's being modified is a verb like "come" or "take," and it really won't be grammatically wrong if we did that. After all, it's an adverb--particularly since it has a "-ly" as its tail--that's supposed to modify a verb. However, to say “Words don’t come easily” and "Take it easily on yourself" somehow has a false, unspontaneous ring to it, and--if I may be so bold to add--not melodious and not singable at all. I think this is an excellent case of effortless, euphonious usage trumping excruciatingly straitlaced grammar.
(http://josecarilloforum.com/imgs/words-don't-come-easy_heart-1A.png)
For perspective about the song “Words (Do Not Come Easy)” referred to by Forum member Maria Balina, its lyrics were written and its music composed in 1982 by French-Tunisian singer F. R. David (his full name is Elli David Fitoussi). As sung by F.R. David himself, it sold 8,000,000 singles worldwide and topped various charts around Europe in late 1982, then went on to become the 22nd best-selling single in the United Kingdom in 1983.
Below are the full lyrics of the song:
Words
(Lyrics by and sung by F.R. David, 1982)
Words don’t come easy to me
How can I find a way to make you see I love you
Words don’t come easy
Words don’t come easy to me
This is the only way for me to say I love you
Words don't come easy
Well, I’m just a music man
Melodies are so far my best friend
But my words are coming out wrong
Girl, I reveal my heart to you and
Hope that you believe it’s true ’cause
Words don’t come easy to me
How can I find a way to make you see I love you
Words don’t come easy
This is just a simple song
That I’ve made for you on my own
There’s no hidden meaning you know when I
When I say I love you honey
Please believe I really do ’cause
Words don’t come easy to me
How can…
You can watch and listen to this YouTube recording of “Words” as sung by F.R. David himself in what’s described as “a catchy, slightly plaintive synth-led mid-tempo ballad sung in a slender, high-pitched voice.”
CLICK LINK TO PLAY YOUTUBE VIDEO:
“Words (Do Not Come Easy)” (https://www.youtube.com/watch?v=5nG1Ka7BXaw)
(http://josecarilloforum.com/imgs/words-don't-come-easy_song-recording-1A2.png)