You are welcome
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I think the "prelisten" checkbox is there to listen to the song, while you change the settings on the fly... like adjusting the levels and hearing the changes in the sound. Without prelisten... you have to change the settings, save them, and then listen to the song to see how it sounds. But with prelisten, you can listen to the song, while you are making the changes. This is what I think it should be.
"Prelisten" is not getting enabled on my PC, I don't know why.
Yes, 1by1 seems to be quite a gem. Such small size, and yet so configurable. There are other such small players too. You can check out Foobar2000, XMPlay, and Xion. These players too have got fairly small size, but are no less than other audio players.