Hi,
The reason that is being rejected is there needs to be a forward slash ('/') right before the closing bracket at the end of the sample tag as follows:
<sample rootnote="82" path="samples/intro.wav" />
Unfortunately, the XML parser is very finicky about correctly formed XML. If you ever have any questions about your XML, you can drop it into this XML validator here and you should get an error message explaining why it's not valid.
– Dave