Major 7th chords and other added note chords are like strong spices. Your have to use them sparingly and judiciously, otherwise, their flavor can be overpowering. It's characteristic that someone who learns a new type of chord (such as a three-chord folkie suddenly discovering major 7th chords and thinking they're real cool) tends to overuse it and/or use it injudiciously until they grow the brain cells necessary to handle it—if they ever do. If used as passing chords or to add a bit of emphasis at a particular point in a song, they can add just the right amount of salsa, and you hardly notice they're there—but you'd miss them if they weren't.

As I mentioned on another thread, I use an Fmaj7 as the second to last chord in each verse in a modal version of The Braes of Yarrow. I'm coming from an Am (the tonic), and I will be returning to an Am. The note I sing at that point is an E, and it's on the beat. I have my choice of staying on the Am (dull), playing C (really bad), or playing the expected Em (big yawn). I play the unexpected Fmaj7—hold it for a second—then resolve it to the final Am. And it sounds like it belongs there!

Out of a repertoire of several hundred songs, I use major 7th chords in maybe three of them. It's not folkie, it's not traditional, but musically, it works. And nobody, including folkies, gives me any grief about them, because they slide right in, nobody recognizes them as major 7th chords, and they sound right at that point. But—ya gotta know what yer doin'!

Don Firth