Well, what about theater? On stage, contemporary shows are using more and more pre-recorded scores -- including underscoring throughout the show. And this is not just for Musicals. As a musician, I am a bit dismayed at how so many professional theaters are no longer employing pit orchestras of any size. But I am even more dismayed at the use of underscoring throughout the entire show. When used by professionals (sound boards and engineers and lavalier mics on all of the actors), the through-underscoring is effective. However, in the less endowed productions, the underscoring can be a DISTRACTION OF EPIC PROPORTIONS!
I recently went to see two middle school Musicals "Into the Woods Junior" and "Once on This Island Junior." Both had pre-recorded Soundtracks with underscoring throughout -- that means that all of the narration and most of the dialogue was delivered over the soundtrack. Where this is an enhancement when adult cast members have sufficient personality and talent and skill to project and emote past the footlights, the little 10-13 year-olds with little experience couldn't compete.
Imagine yourself as the grandparent who dutifully comes to see the grandchild in the school musical. You have had no exposure to the music or story of the show. You have no idea about how to distinguish one character from another because the costumes are not too helpful and the kids all look and sound juvenile. The acting, singing, dancing and staging are only as good as the kids' emerging talents allow. The school has a tight budget, so sets, sound, lighting, and backstage communications are dismal at best. The auditorium is noisy with bad acoustics, noisy babies crying, and rustling of people and chairs. Then add to the mix CONSTANT MUSIC and SOUND EFFECTS on a pre-recorded track. You really have no hope of understanding, let alone enjoying, this production at all!!!!!
My advice to directors that want to use pre-recorded soundtracks with underscoring throughout every scene --- CUT THE UNDERSCORING! There is usually a clause in the contract that states that you may discreetly CUT material from the show as necessary to accommodate your particular situation. That usually means that you may cut or adjust lines when they are too difficult or you have to change the blocking or delete names because you don't have enough characters, and stuff like that. But you can also just NOT PLAY the underscoring throughout every scene.
It will help your audience understand the show so much better!