AthTek Free Voice Changer is a handy audio tool for Windows users. It has a very clean interface without any exaggerated color and overstated features. It clearly lists 4 steps for you to obtain the sound effects you want.
Hanso Player is an audio software offering great features like a smart interface, net streaming, mp3 wav converter, an integrated ID3 editor which makes renaming and changing files easier. It supports MP3, FLAC, AAC, MP4, WMA formats.