There aren't many applications created exactly for this type of job, but you can find a few that support this operation. For instance, WIDI Recognition System is an application of this type that can help you open MP4A videos and extract the audio to MIDI format. To find more information about it as well as download links, visit the official website of the product. Download the software, install it, add the file, select the output as MIDI and wait for conversion, however, you might need to buy the full product to have a complete extraction of the audio stream.
