Add this function in a subclass to get a notification just before an audio clip is being imported.
This lets you control the import settings trough code.
class MyAudioPostprocessor extends AssetPostprocessor {
function OnPreprocessAudio () {
// Import files containin "mono" in their name as mono.
if (assetPath.Contains("mono")) {
var audioImporter : AudioImporter = assetImporter;
audioImporter.forceToMono = true;
}
}
}