In the song "Eien no tobira" (永遠の扉) by Yonekura Chihiro (米倉千尋) the chorus starts with this line:
Since じゃなくて is contraction of ではなくて, I would have expected the second clause to say でもなくて, but it became もなくて with the で omitted instead. There is possibility that the lyric writer really wanted to say "there is no my promise either" instead of "it is not my promise either" but that would make it not parallel to the the first clause "it is not my word" (sorry I can't find a better translation for 言葉 in this context).
Assuming if the lyric line's second clause was supposed to say 「約束でもなくて」, is it okay to omit the で particle and yet still retain the intended meaning through parallel structure with the first clause? In the context of a song or literature, does this kind of trick work?
N.B. It is a really nice song. I recommend trying listening to it if you haven't :)