I couldn't place the specific song in question as I listened to it, but it appeared to be an accompaniment track that is absent of the main melody. Such tracks were meant to be played back in support of a singer or instrumentalist who would provide the melody/words at the time it was performed.
Today, we might call such a recording a "karaoke" track.
In the recent comments to the video, it is identified as "My House Is Full (But My Field Is Empty)" which is a song written by Lanny Wolfe and made popular by the Lanny Wolfe Trio.
Now that I know what to listen to, I agree that this is an accompaniment track for that song. The song was recorded and performed by many different Christian singers and also sang in many worship services beginning in 1977 when it was first published and recorded by the Lanny Wolfe Trio.
The lyrics are based on Christ's words recorded in Luke 10:2. “The harvest is plentiful, but the laborers are few; therefore ask the Lord of the harvest to send out laborers into his harvest."