I was reading a forum post
the other on the subject of film music and how it has become poorer due to cheap computers and music software. The guy's main point was that if you spend peanuts you get monkeys. Of course in many ways he is right but there still seems to be a lot of snobbery around the written to script composers; the library composer being more of a poor country cousin. What is interesting, though is many script composers are dishing up plenty of library music or royalty free music
To be fair, library composers are not working to a script so cannot adjust to dialogue et al; they create general moods, ambiances etc and while their equipment maybe cheap it does not negate a composer's' musical abilities. Secondly even composers lucky enough to be working to a script will have to have pieces "ducked" in places. Ducking, if yo do not know, is automatic compression applied to one audio source (i.e the music) so you can hear one of the other audio sources (i.e the dialogue).
The digital age has changed so much for musicians and film makers alike, it seems anyone can do either these days but one idiom always remains true: the cream always rises to the top. It is not all black and white though, some library composers are really on the money and some, mainly the inexperienced fall into the classic pitfalls of trying to master their own material and even upto 0dbs (mixed down material should not go above -6dbs).
The problem is musicians/composers do not really know how to master or normalize music though some appreciate what skills are required. Sure there are plenty of plugins out there that can used for these purposes but would you give the keys of your car to a blind man?
Crucially most studios and home studios will not give you properly mastered gear, because it is not their job (it is expensive and beyond their abilities). So buying something off some website, it may sound good, it probably is good but mostly it will not have graced the confines of a pucca mastering suite where all that mud, screeching highs and exaggerated bass can be controlled and refined. Composers should be working and mixing down to 24bit/96kz. Most studios, even home studios are at least mixing down to 24bit/96khz these days... 48khz is not so common these days but in terms of mix down quality, you may occasionally get higher quality if you ask: 24bit/196 khz though the project has to started at these rates, you cannot convert up and expect things to sound better. Though it is argued that 192khz is a salesman gimmick as no one seems to hear the difference between audio recorded at 24bit/96khz and 24bit/192khz.
Properly mastered audio will playback fine on any system. If you've got pops and clicks then, as is usually the case with cheap solutions, someone has not done their job properly (remember to crossfade guys)... you need GOOD headphones to hear some pops and clicks - like some sennheiser HD 650s. That said, getting rid of them is another headache.
Bottom end is a problem as it is difficult to gauge if you do not have the right mixing environment or speakers and only a mastering engineer (the guy that makes sure your sound is good) can properly gauge and treat/control frequencies below 80 hz as well as those above. Most music producers/composers are very conservative in this area and "roll off" (eliminate) anything below 40 hz to increase headroom for where the meat is at, i,e the real punch and dynamics. You're getting low now and from there on in it is sweet and pure Sub bass which is a very technical area and knowing how to to side chain and how to use a multi-band compressor is just the start of going "down there" and getting it right, this is not for your typical film guy to play around with.
Happily though, most music does not go below 40 hz.. yeah your action film sound effects, r and b and other types of bassy pop music and dub reggae push the super low end hard and here, of course proper mastering is utterly essential.
So it all comes back to whether the music has been mastered professionally or not. Loads of films out there have amateur recordings plastered all over them (but they've been mastered first) and they cash in on it too.. i.e the punters like that intimate lo-fi sound
: and there is nothing wrong with that unless you are trying to remake "Ben Hur" or "The Sound Of Music".