I am using a Samsung Galaxy Sky with Android version 6.0.1. I have tried at least eight times to use the Replaygain Scanner in the Foobar Mobile app for Android to standardize the volumes of my music (which is all on the SD card); each time it scans the entire library (over 3,000 songs), yet each time nothing changes; all my music sounds just like it did before I ran the scanner. After the most recent attempt (yesterday), I started poking around and looked under Tools/Console; there I found a huge number of tracks listed. Each one said the same thing: "could not update tags on file [name of file/track]...reason: access denied".
I would really like to get my music volumes adjusted so I don't have the volumes all over the place. Any advice on what I might be doing wrong or overlooking?