Applescript 无法将文件名导入别名

这是苹果书

tell application "iTunes"
set new_playlist to get first user playlist whose id is 20721
set nexttrack to (add(POSIX file ( get "/Users/paul/tmp/Music4/My Bloody Valentine - m b v - 2013 [FLAC][24-96][WEB]/09 Wonder 2.flac") as alias) to new_playlist)
set trackname to name of nexttrack
end tell

失败于

javax.script.ScriptException: The variable nexttrack is not defined.

我认为前面的线路有问题，但我看不出有什么问题。（注意，起点是unix/notation中提供的文件名）

尝试：

set songAlias to alias (POSIX file "/Users/paul/tmp/Music4/My Bloody Valentine - m b v - 2013 [FLAC][24-96][WEB]/09 Wonder 2.flac")

tell application "iTunes"
    set new_playlist to get first user playlist whose id is 20721
    set nexttrack to add songAlias to new_playlist
    set trackname to name of nexttrack
end tell

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这可能会产生一些不同，我不确定是否会被标记为正确。但我在我的例子中意识到我使用的是flac文件，而iTunes不支持flac。