Synced Lyrics for AI Songs: How Each Line Is Timed

What every song with words comes with

Open a song that has lyrics, in your library, in the studio once it finishes, or on its share page, and the lyrics box under the player follows the music. The line being sung is highlighted, the lines already sung fade, and section labels such as [Verse] and [Chorus] sit above their lines as small headings that never light up. The share page shows the same box, so the people you send a song to see it too.

The same timing leaves Tunely three ways. From the song's ⋯ menu, any signed-in account, free plan included, can download it as an .lrc lyrics file or an .srt subtitle file, at no cost. The music video made from a photo ($6.99) burns it into the picture as captions, and so does the lyric-video export on Pro.

Two kinds of song have no synced lyrics: instrumentals, and covers of an uploaded recording made without pasting its words, because the engine does not report which words it sang. Paste the lyrics into a cover and it gets them like any other song.

Where the timing comes from

When a take finishes, the music engine lines the lyric up against the vocal of that exact take and returns every word with the second it starts and the second it ends. Two takes of the same lyric get two different sets of times, because the singer phrases them differently. The lyric's own line breaks and [Section] tags come back attached to the words, so the lines on screen are always the lines of the lyric, never a guess.

Here is the moment our demo song tripped over, as the alignment reports it. The ⏎ marks the line break, which the engine attaches to a word.

The line break rides on “river”, the last word of the first line, and the singer holds that word for more than three seconds. The second line, “The rain came down like it had somewhere to be”, begins at 22.66 s.

The rule: a line starts when its first word is sung

Until 20 October our code started each new line at the word that carried the line break. That word is the last word of the previous line, so “The rain came down” was given 19.32 s, the moment “river” began, and lit up 3.3 seconds before anyone sang it. The same happened after every held ending, which is exactly where the gap is longest.

The fix is a single rule, applied to every song made since: a line starts at its own first word. If the word that carries the break also carries the start of the next line (the engine joins a section tag to the next word, as in “[Chorus]⏎We”), that word's time is used; otherwise the next word's. Spotify gives artists who sync their own lyrics the same instruction: “Sync each line when the first word of the line is sung.”

Two smaller rules came with it. A section label now starts with the first line under it, so it can never take the highlight away from a line still being sung. In one of our songs the first verse's label started together with a five-second held “whoa”, so for the whole “whoa” no line was highlighted; the line itself had lit up early, during the word before it. And line times are now measured against the take's exact length, 99.6 seconds for this song rather than a rounded 100, because the player multiplies them by the length of the file it is playing. The rounding alone had moved lines up to about a third of a second, early or late, near the end of a song.

The first line of each section was already right, because the [Verse] or [Chorus] tag and that line's first word come back as one piece. The lines that follow a held ending were the ones that ran early. The [Chorus] label itself used to light at 28.92 s, on the held “be” that ends the verse, which left no line highlighted for the whole 3.6 seconds of that note.

How we measured it

We kept the word timing of five songs we made on our own test account and played each one the way the song card does: at any moment the highlighted line is the last one whose start has passed, shown 0.2 seconds early so your eye arrives with the singer. For every sung word we checked whether its own line was the one lit a tenth of a second into the word. The next line lighting within its 0.2-second lead counts as right; that lead is measured from when the next line is really sung, not from its stored start.

Of the 183 sung lines, 145 now start later than they did, by 0.58 seconds in the middle case. Forty-eight moved by one to four seconds and two by more than four; the largest, 5.33 seconds, is a line in the birthday song that follows a long held note. No line moved earlier.

What this check cannot show is whether the alignment heard every word right, because it takes the alignment's own word times as the truth: it proves the lines now follow the words, and a word the alignment places wrongly stays wrong. The alignment reports a character error rate for each take, and on these five it ran from 12% to 33%, highest on Lazy Saturday at the Beach.

When the timing is missing or off

The rule fixes how lines are built from the word timing. A few things can still put a highlight in the wrong place, and each has a tell:

• Not ready yet. A finished song is sometimes delivered a moment before its word timing. The lines are then spread evenly, and the real timing is fetched the next time the song is opened in your library or on its share page (at most once a month per song).
• A block placed wrongly. Now and then the alignment puts a passage in the wrong place. In one song we checked, a copy of the first verse was timed inside the instrumental intro, so the opening lines lit up before any singing. If the highlight runs ahead in the first seconds of a song, this is the likely cause; the fix is to move those lines in the .lrc or .srt.
• Repeats and ad-libs. When the singer repeats a line the lyric has only once, or ad-libs between lines, the line stays lit through the repeat.
• Songs made before 20 October 2026 keep the earlier timing: a line that follows a held note can light up early, usually by under a second and by up to about five seconds after a long one. Their .lrc and .srt files carry the same times.

Using the timing outside Tunely: LRC and SRT

Both files come from the song's ⋯ menu and hold the sung lines only; section labels are left out.

Spotify takes synced lyrics from Musixmatch rather than from a file you upload: outside Japan, you add and sync them in a free Musixmatch account linked to your Spotify artist profile, and the .lrc gives you every start time to copy. Releasing a song there needs commercial rights, which come with Pro or Ultra.

To change a time by hand, open the .lrc in any text editor and edit the number in brackets, or the start and end of a subtitle in the .srt. The [ar:] line at the top of the .lrc says Tunely; put your artist name there before you share the file.

Checklist for clean synced lyrics

Most timing problems start in how the lyric is written. Before you generate, and once after:

• Write one sung phrase per line. The highlight moves a line at a time, so a line that runs across two breaths stays lit for both.
• Put section tags on their own line in square brackets: [Verse], [Chorus], [Bridge]. They become the small headings in the lyrics box.
• A direction in brackets on its own line, such as [guitar solo], shows as a label and is never highlighted; one inside a sung line stays visible as part of that line.
• Play the first verse and chorus once. If lines light up before the singing starts, a block was placed wrongly; fix the first times in the .lrc.
• For a music video, start the clip on a sung line rather than in an instrumental gap; the default start is the chorus.
• Download the .srt for YouTube and video editors, and the .lrc for music players and Musixmatch.