This is LyriCue, the audio lyrics prompter.
If you write your own songs, there's a specific moment LyriCue is really good for: you're working on a new song and you haven't fully memorized it yet, but you want to sing it while playing your instrument, or play it for someone, or try it out at an open mic, or run it at a co-writing session. Instead of holding a printed lyric sheet or squinting at your phone, you can paste your new lyrics into LyriCue, or just dictate them, and have LyriCue read them back to you line by line as you play, right up until the song is second nature and you don't need it anymore. Turn on spoken chords while you're still getting the changes under your fingers, and turn them off once you don't need the reminder.
It's also just a fast way to get a rough idea out of your head and into something you can actually perform, without stopping to write everything out neatly first.
If you're building your own lyrics file, the most important thing to think about isn't how long a line is on the page, it's how long a phrase is when you sing it. How much can you actually remember and sing before you need the next chunk? What groupings of words make sense as one unit?
On the page, a song is usually laid out in lines, often lines that rhyme. But when you actually sing it, a printed line often splits into smaller pieces, for rhythm, breath, or just how the phrase falls. LyriCue can read a whole line at a time, or break lines up by word count using the Lines setting (Short, Medium, or Long), but it has no way to know how you actually sing any particular line.
The most reliable fix is to build that into the file itself: put your own line breaks where you naturally pause or breathe when singing, so each line is already a singable chunk by the time LyriCue reads it. If you'd rather not do that, try the Short, Medium, or Long line length settings and accept that LyriCue may split a line in a slightly odd spot here and there, or turn line breaking off entirely and just hear each line exactly as it's written in the file.