Maybe your Sound Recorder is configured to save the sound files in your phone memory. If so then change it to Memory card from the settings.
And if it still not working then maybe your sound recorder is optimized for sending MMS. Video & Sound recorders are optimized for MMS by default and hence they can record for only few seconds so that you can send those files over MMS easily. If so then you can change it also from the settings.
Let us know if it works. Thanks.