MIDI stands for Musical Instrument Digital Interface (Musical Instrument Digital Interface). This is a standard serial communication protocol that allows computers, synthesizers, sequencers, controllers and other electronic musical devices to communicate and share information to generate sounds. This information defines various data types such as numbers may correspond to particular notes, numbers synthesizer patches or driver settings. Because of this simplicity, the data can be interpreted in various ways and used for purposes of music. The protocol includes additional hardware and software specifications.
The AAC file type is primarily associated with 'MPEG-2 Advanced Audio Coding File'. Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for digital audio. AAC is promoted as the successor to the MP3 format by MP3’s creator, Fraunhofer IIS. AAC’s most noted use is as the default audio format of Apple's iPhone, iPod, iTunes, and the format used for all iTunes Store audio (with extensions for proprietary Digital Rights Management (DRM) where used).