Any suggestions would be appreciated.

You can see the message comes from inside SOAP::Lite

 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" associates the prefix xsi with a namespace(url)

If you go to http://www.w3.org/2001/XMLSchema-instance you'll find http://www.w3.org/TR/xmlschema-1/#xsi_type

So, whatever schema/wsdl/xml is in play doesn't specify what is audioTrackVO -- unknown type is unknown, can't be decoded

why this happens? error in the wsdl/xsd or the response or SOAP::Lite? Impossible to know. I'm guessing SOAP::Lite plays a part (needs your help to load schema or somesuch ), but XML is so complicated and 98% of everybody gets it wrong, its hard to say without lots more details (250% more)

I suggest you try the latest version cpanp -i PHRED/SOAP-Lite-1.0.tar.gz but that probably won't change anything

Better idea is to try SOAP::Simple cpanp -i BERLE/SOAP-Simple-0.00_03.tar.gz, see if SOAP::Simple works for you for this

SOAP::Simple is simple :) but its built by something very much SOAP (complex), its XML::Compile::SOAP/XML::Compile::FAQ/https://www.ebi.ac.uk/Tools/webservices/tutorials/06_programming/perl/soap/xml-compile-soap/XML::Compile::SOAP/http://perl.overmeer.net/xml-compile/#doc

You might also like How to Call a .NET-based Web Service Using the SOAP::Lite Perl Library, Contact Webservices on Microsoft Exchange Server , An XML Overview Towards Understanding SOAP, it might help you gain a better understanding of SOAP/XML which will help you figure this all out

I hate SOAP, really :)