Has technology improvement caused film music to change?
When watching older films (by older, I mean before 1970), I always notice the lack of strings in the soundtracks, and when there are strings, they never play quietly. For example, in Mary Poppins, the music is mostly brass and percussion, with strings only occasionally appearing, while Jurassic Park makes extensive use of a cello and french horn motif. Most modern scores (excluding ones composed of pop music or in pop music style) seem to use much more diverse instrumentation than scores from fifty years ago.
I believe strings are typically more difficult to record than brass and recording technology has significantly improved recently (I confirmed this by comparing the B section of the main theme from Star Wars as recorded for Episode IV (1977) and Episode I (1999), the latter having much better string quality).
Has this improvement affected how composers orchestrate their music? Specifically, has it made them more willing to use strings? On a side note, I've noticed the same effect with the french horn. Is this at all related?
Certainly, technology has caused film music to change, just as it has cause music in general to change. Consider: early jazz band relied on tubas and banjos because neither a string bass nor a guitar could be heard on acoustical recordings. When electrical recording came along, the modern jazz rhythm section was born. As amplification technology improved, pianists like Teddy Wilson replaced the likes of Earl Hines and singers like Billie Holiday replaced the likes of Kate Smith.
Movie composers live in the world, and certainly they would be as interested in and influenced by evolving technology as anyone else in music or anyone else in movies. But mainly, the technological developments that are most exploited these days have less to do with recording technology and more to do with sound production. In other words, the question is less "How do we record a string section that will sound good for this scene?" and more "How do we produce a sound like that of a string section?" A single soundtrack may include a symphony orchestra playing Beethoven, a didgeridoo, a cool jazz quintet, an African drum ensemble, and any number of purely electronic sounds all created within the same studio on the same synthesizer by one person. Modern technology has vastly increased the choices open to a single musician at any given moment, and allowed for a variety of timbres, rhythms, and cultural associations that has never been possible before. Here is a link that might interest you:
And by the way, if you watch movies from the 1930s, you will hear no end of strings.