Positive game-changers in your progress
General mountain dulcimer or music discussions
Wout, I think you have the main idea, but you might be thinking too literally. In common American parlance, a "game changer" is an idea, technique, or event that significantly changes the manner of doing something.
So Jan was asking people what they had discovered in their own dulcimer development that significantly changed in a positive manner how they were playing and learning the dulcimer. So yes, indeed, it is a matter of growth. But not the slow, incremental type of growth that you might get from practicing scales every day, but the growth that comes from a specific change that leads to a big leap in your understanding or ability.

The West Virginia fiddler Ernie Carpenter wrote the song (in the 1950s, I think) and you would expect it to be under copyright. However, I have not found any evidence that the song is copyrighted, and everyone (not just dulcimer players) seems to both credit Carpenter for its composition and also post music and tablature freely.
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I also just checked some of the consumer reviews. Lots of complaints about the smell. I don't remember it being that bad, but we keep ours in the garage, so it probably aired out before we ever had to use it.