80's Young Adult Science Fiction Book With Cassette

I've been searching for this for years. I can only recall the following:

Early 80's (possibly late 70's). Young adult short story book with hand drawn illustrations Was a book on cassette, a follow along type Science Fiction story that ends where the two main characters, a man and woman, are left on a new planet to populate A third main character is killed fighting off an attack The most interesting feature was the production quality - it was complete with sound effects, different voice actors, and this really haunting sci-fi score that I thought sounded very close to the Amityville Horror theme music.