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; } } }