Do not be lazy and put an entire song on your screen at one time. Four lines of text is a balanced choice when determining how many lines should be presented on a single worship slide. Four lines is ideal because it leaves the screen uncluttered and easy for your community to find their place whether they are familiar with the song or not. Like everything else in your presentation, you want every line of text to be easy to find, clearly readable and not crowded in any way.
Two or three lines of text is also acceptable if you have less than four lines of text to present at one time. If you are using lyrics over IMAG, it is common practice to use only one or two lines of text when presenting lyrics. Fewer lines of text take up less screen real estate and make it easier for your community to find their place during times of worship. Projection operators will need to advance to the next slide more often as the number of lines of text decreases per slide.
The maximum number of lines per worship lyric slide is five. Exceeding this number puts too much text on your screen at one time and makes it difficult for your community to find their place. If the lines of text are very short, then having five lines is a reasonable choice. In most cases stay within four or fewer lines of text.
The tempo of a song will also influence the number of lines you choose to present at one time. It is good practice to place more lines of text on your slides for faster songs and fewer lines of text for slower songs.
An alternative school of thought believes that presenting more lines of text on your screen at one time will help your community see the story in a song and give more time to meditate on its words. When an audience only sees small portions of a song at one time, they may be less likely to appreciate the full narrative of the song. This is something to consider when choosing how many lines of text to project per slide. For more contemplative and reflective songs you may consider increasing the number of lines of text on your screen if you think it is appropriate.
To learn more worship lyric projection best practices read The Worship Media Handbook.