Indeed, equal temperament puts the notes out of tune but gives us the ability to transpose the song and have it sound right.
With my sax, I use my ear and lip pressure. Sometimes even intentionally out of tune for effect. I'll do the same on guitar at times, although I find it easier on the sax. But then I've been playing sax since I was a child.
As long as it sounds good to me, I'm OK with it.
Some old rock songs that have out of tune guitars wouldn't sound as good if they had invented electronic tuners back then, :D
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