What karaoke does
When a song starts, its lyrics appear line by line. The current line is highlighted and the text moves along on its own, in time with the singing. Nothing to start or to synchronise: if the song has lyrics, they follow.
Which files to provide
You need one lyrics file per song. It is the same kind of file that ordinary music players use to show lyrics — an .lrc file. You will find them on lyrics websites, or with a free tool such as LRCGET, which fetches them for your whole library on its own.
Where to put them
The simplest way: drop the lyrics file next to the song, in the same folder and with the same name. That is where lyrics tools write them anyway, so you have nothing to move. If you would rather not mix lyrics in with your music, gather them in a folder called .karaoke at the root of your library, laid out the same way — one folder per artist, then per album.
Switching karaoke on
Turn it on in the settings, Karaoke section. A microphone button then appears in the top bar: that is what shows or hides the lyrics, and its state carries over from one song to the next and from one session to the next.
With one screen or two
On a two-screen setup, the lyrics take the second one while the library stays available on the first: you keep picking the next songs while someone sings. With a single screen, they go full screen, with a button to hide them and return to the library. The colours follow whichever theme you have chosen.
If the lyrics do not keep up
A lyrics file is timed against one particular version of a song. If it was written for a different edition from yours — a live take, a remix, a shorter radio edit, a remaster — the lyrics will run beside the singing, sometimes by several seconds. That is not a fault in the application: the file simply does not match your recording.
Worth knowing
How well the lyrics track the singing depends entirely on the file. With an ordinary file, the current line lights up as a whole — and that is deliberate: a line is often sung in two seconds and followed by silence, so colouring it word by word would leave the colour trailing behind the voice. With a more detailed file, where every word carries its own timing, the colouring really does follow the singing.