Yep, with the as3cf_pre_upload_attachment filter.
https://github.com/deliciousbrains/wp-amazon-s3-and-cloudfront-tweaks/blob/beb2e0f1bba71be7b462a60209e5ff630a57437e/amazon-s3-and-cloudfront-tweaks.php#L528
The above example stops movies from being offloaded, you can turn it on its head and replace this line…
if ( is_string( $extension ) && in_array( $extension, array( 'mp4', 'mov' ) ) ) {
… with …
if ( is_string( $extension ) && ! in_array( $extension, array( 'mp3' ) ) ) {
I’ve left the array bit in just in case you decide to add other types of audio files.
You could do something else such as get the mime type and only offload any type where the first part is “audio” etc.
-IJ
