20. The computer-readable medium of claim 19 , where the one or more instructions to generate the keyword include: one or more instructions to obtain an audio file corresponding to the audible feature, one or more instructions to obtain information based on analyzing the audio file, and one or more instructions to generate the keyword based on the obtained information, where the one or more instructions to obtain the information based on analyzing the audio file include: one or more instructions to play the audio file, and one or more instructions to obtain the information based on playing the audio file.
19. The computer-readable medium of claim 17 , where the instructions further include: one or more instructions to generate a keyword based on the audible feature of the document, the audible feature corresponding to: an indication of whether a sound is generated when the document is rendered for display, an indication of whether music is generated when the document is rendered for display, a name of music that is generated when the document is rendered for display, or a name of an artist that is associated with music that is generated when the document is rendered for display; and one or more instructions to associate, in the index, the keyword with the information identifying the document, where the plurality of terms further includes: a term identifying the keyword that is generated based on the audible feature, and a term to be searched in relation to: the indication of whether a sound is generated when the document is rendered for display, the indication of whether music is generated when the document is rendered for display, the name of music that is generated when the document is rendered for display, or the name of an artist.