I'm with you, bert. Your non-gratuitous changes are what I call "making it your own". When I sing a song, I often "hear" something that sounds (to me) exactly like the person I learned the song from. Since these singers range from Gordon Bok to Rosalie Sorrels, it'd be pretty spooky if anybody else heard that resonance. At the other extreme, the spookiest thing I've ever heard on a folk stage was a performer who took (as far as I could tell) ALL of his material from another, more famous performer, and didn't make the slightest change in phrasing, pacing, anything. He wasn't doing an impression or an imitation, it was more like a medium or channeler, except that the other performer was still alive. Brrr. A happier memory is hearing four guitarists who'd each worked out their own transcriptions of Scott Joplin's "Entertainer", all playing together. The individual differences went together beautifully. Long live making the song your own, and long live variants to choose from.