Some Wikipedia articles include sound or video files, which can be played on almost all personal computers. However, your computer must have the right software. If your computer does not automatically play these files when you click on them, downloading and installing free software from the internet can enable it to do so.
Sound files on Wikipedia generally use the Vorbis audio format, and video files use the Theora format, both contained in an Ogg file. These are analogous to other formats used to play digital audio and video such as MP3 and MPEG. However, Microsoft Windows and Mac OS X do not support these formats by default, and require additional software to play them (see below).
Music files may occasionally use the MIDI format (.MID or .MIDI extension). MIDI is generally playable without additional software, as most computers have a MIDI-enabled player and sound card.