Technically yes, but you may want to consider things like adding a password and limiting the allowable file size.
Keep in mind that the password will be sent in the clear (i.e. no https) so is not resistant to "man in the middle attack" but will stop casual unwanted uploads by others.
Since you will be adding the header before hand, it makes sense to do some basic checking in the script to ensure the file being uploaded is at least a wav file.