Take a look at resampling the files with SOX.<br>
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Google is your friend :<br>
<a href="https://www.google.com/search?q=sox+change+tempo&ie=utf-8&oe=utf-8">https://www.google.com/search?q=sox+change+tempo&ie=utf-8&oe=utf-8</a><br>
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-- <br>
Sent from my Android device with K-9 Mail. Please excuse my brevity.