ExternalStorageDirectory

kt

var externalStorageDirectory = Environment.getExternalStorageDirectory().toString()
var externalFilesDirMusic    = getExternalFilesDir(Environment.DIRECTORY_MUSIC).toString()
var externalFilesDirs        = getExternalFilesDirs("/")

Log.d("x", externalStorageDirectory) // => /storage/emulated/0
Log.d("x", externalFilesDirMusic)    // => /storage/emulated/0/Android/data/com.example.myapplication/files/Music
Log.d("x", externalFilesDirs.joinToString(", ")) // => /storage/emulated/0/Android/data/com.example.myapplication/files
                                                 //  , /storage/63C5-517B/Android/data/com.example.myapplication/files

var sdCardDir = externalFilesDirs[1].toString().replace(Regex("/Android/.*"), "")

Log.d("x", sdCardDir)
for (file in File(sdCardDir + "/MUSIC/Music").listFiles()) {
    Log.d("x", file.toString())
}