How MIDI Karaoke Files Embed Synchronized Lyrics

MIDI karaoke files, typically bearing the .kar or standard .mid extension, synchronize text with music by storing lyric syllables as timestamped meta-events directly alongside musical sequence data. By leveraging the delta-time timing engine of the Standard MIDI File (SMF) specification, karaoke players read lyric text events in real time and display them synchronously with the corresponding vocal melody notes.

The SMF Container and File Structure

A MIDI karaoke file is almost universally structured as a Standard MIDI File (SMF) Type 1. Type 1 files contain multiple parallel tracks playing synchronously against a shared tempo map.

In a standard karaoke file, standard musical tracks contain note, instrument, and controller data (such as drums, bass, and piano), while one or more tracks are designated to handle vocal melodies and synchronized text.

Lyric Meta-Events (FF 05 and FF 01)

MIDI protocol reserves non-musical data transfers for "Meta-Events," designated by the status byte 0xFF. Synchronized karaoke systems rely primarily on two specific meta-event types:

• Lyric Event (0xFF 05): The official standard for karaoke text. An FF 05 event contains a length indicator followed by the text string (in ASCII or encoded formats) for a specific word, syllable, or character.
• Text Event (0xFF 01): A generic text event used by older sequencers or alternative karaoke engines to display comments, author information, or full lines of lyrics.

Delta-Time and Syllabic Timing

Synchronization is achieved using MIDI's native timing mechanism: delta-time. In a MIDI sequence, every event is preceded by a variable-length quantity indicating how many "ticks" have elapsed since the previous event.

Instead of embedding entire sentences as a single block of text, sequencers break words down into discrete syllables. Each syllable is assigned its own FF 05 Lyric event and placed at the exact delta-time corresponding to the Note On event of the lead vocal guide track. For example:

• Tick 0: Note On (Pitch C4) + Lyric Event: "Hel-"
• Tick 240: Note On (Pitch D4) + Lyric Event: "lo "

Because the text event shares the timestamp of the pitch, the karaoke playback engine knows precisely when to display and highlight each syllable on screen.

Layout and Flow Formatting Conventions

Because standard MIDI tracks have no native graphical display capabilities, karaoke specifications (such as the widespread Soft Karaoke standard) embed special control characters directly into the text strings to handle visual formatting:

• Line Breaks (/): A forward slash preceding a syllable instructs the player to wrap to a new line on the display.
• Page Clears (\): A backslash clears the current screen of text to prepare for the next verse or chorus.
• Header Tags (@): Text events beginning with @ typically contain track metadata rather than performance lyrics (e.g., @T for Title, @A for Artist, and @V for Version).

By combining standardized delta-time scheduling with syllable-level FF 05 meta-events and simple display-formatting prefixes, MIDI karaoke files deliver lightweight, accurately synchronized lyrics within a standard sequence track.