This article in The Atlantic is a Songwriting Masterclass from Wilco's Jeff Tweedy:
"One of the primary ways I write lyrics is to sing and record vocal sounds without words, vowel and consonants that sound like language but don’t actually mean anything. I’ll even double vocal tracks of these sounds without words—I call them “mumble tracks.” A lot of times people will hear them and think I’m singing real lyrics there, but I’m not. I mix them low so you have to struggle to hear, but loud enough so you can get the sound you want and get the melody to come through. With this approach, you can work on a song and finish it without even having the lyrics done."
Lyrics are one of the toughest things for me, and there's a lot more in the article: It's worth a read:
Jeff Tweedy's Subconscious Songwriting - The Atlantic
"One of the primary ways I write lyrics is to sing and record vocal sounds without words, vowel and consonants that sound like language but don’t actually mean anything. I’ll even double vocal tracks of these sounds without words—I call them “mumble tracks.” A lot of times people will hear them and think I’m singing real lyrics there, but I’m not. I mix them low so you have to struggle to hear, but loud enough so you can get the sound you want and get the melody to come through. With this approach, you can work on a song and finish it without even having the lyrics done."
Lyrics are one of the toughest things for me, and there's a lot more in the article: It's worth a read:
Jeff Tweedy's Subconscious Songwriting - The Atlantic