Why did Silent Running have songs written for it?

From a different perspective I'm going to suggest the reason was more mundane : money.

Scenario A.

• purchase rights to use existing songs in your new movie
• result : money goes out the door in the form of the initial cost and/or ongoing fees.

Scenario B.

• pay to have songs written for your movie
• result : initial fee, but you get to keep any and all revenue (or some slice of it) from later e.g. radio plays, record sales and performances.

I don't know about you, but wearing my Imaginary Film Producer Hat I'd prefer the B option. :-)

From an artistic point of view there was a desire to have music that reflected the movies themes and Joan Baez was, as it were, the Man for that job. :-)

It's just a matter of what kind of risk-reward model you want for your business after that.

Silent Running was an independent film by big studio standards at the time and the studio was 100% hands off on it.

While other answers here focus on the mood of the film and Joan Baez’s song — and the motivation behind getting that song made — Silent Running was part of an experiment by a major studio to just throw money at good creatives and see what happens.

To understand how a futuristic science fiction film like Silent Running was made, one must take a serious look at the film industry in the early late 1960s and early 1970s.

In short, the film industry was tanking hard. And none of the old time formulas worked when it came to creating movies that get people into theaters. Younger movie goers just did not like what Hollywood was pumping out at the time.

Then in 1969 Dennis Hopper’s Easy Rider comes out. It was effectively a personal project by Dennis Hopper that had a filming budget of $360,000 to $400,000. And when it was released it took in $60,000,000 in 1969 money. That is massive, to say the least.

So suddenly, Hollywood studios wanted in on the independent counter-culture market that fueled the ticket sales to that film. This leads to tons of “weird” films that came out in the 1970s — look at Taxi Driver; how crazy was it that a film like that was made back then — and Universal Studios/Pictures deciding to do the following: Fund five film projects by independent and non-mainstream directors for $1,000,000 each and see what happens.

It was a weird gamble as explained in this A.V Club article:

“After Easy Rider’s success, the major movie studios were at a loss. They knew there was a vast audience of young moviegoers, energized by the counterculture and intrigued by the explosion of European film. For this brief, disoriented moment, the studios admitted they had no idea how to reach this new audience, and their best shot was in giving free rein to those who might. Universal tried and failed with Monte Hellman’s Two-Lane Blacktop—or more precisely, tried and then stopped—but they decided to give the idea another shot, giving five young directors carte blanche, or at least as much freedom as their minuscule budgets could buy.”

And then in this blog post on “Craig Skinner on Film” where Douglas Trumbull talks about the film and the budget provided; bold emphasis is mine:

“We had only one million dollars to make a movie and they would not intervene in any way, they would not look at dailies, it was a complete sociological experiment on behalf of the management of Universal Studios. There were five films made, each for about a million dollars, and Silent Running was part of the package.”

This is key. For a Hollywood studio of any kind to throw money at you and say, “Here! Do what you want and we won’t tell you otherwise…” is a big deal. So yeah, Douglas Trumbull negotiated with Joan Baez to create a song for the film that fits his vision.

But I am pretty sure if he did not have the level of freedom Universal gave him, he would have not have even thought of getting a custom song written and recorded for a film.

So creatively he was freed from any studio interference and complaints. But that said, the biggest part of the filing budget for Easy Rider. That was $360,000 to $400,000. But that was not the total cost of film. The larger part of the budget — that was more than double that filming budget — was the $1,000,000 that was spent solely on music rights.

Knowing that, one can easily assume that creative freedom motivated and inspired Douglas Trumbull to get Joan Baez to write and perform that song. But knowing that licensing rights alone for many films can decimate a film’s budget, why risk doubling or tripling your film’s budget to license music?

That said, if you are looking at the film as typical, modern studio film, the chances of whatever song of the moment being forced into the film are quite high. And major studios nowadays are just huge media conglomerates: A studio producer’s way to save a budget on a modern film is to just go to their company’s music division and get some music that way.

For an experimental film like this it was all on Douglas Trumbull to put it all together. So his vision and passion — as well as his desire to not blow his small budget — all contributed to that song being in the film.

PS: For anyone who cares, the other four of the five films Universal produced this way were:

• American Graffiti (1973)
• The Last Movie (1971)
• Taking Off (1971)
• The Hired Hand (1971)