Resources for the Recording Musician
November 6, 2009

Parallel vs serial compression

I'm wondering if someone could explain what serial compression and parallel compression is, and the advantages of each and when one would be used vs the other.

Serial compression is when the compressor is inserted in the signal chain and you use 100% of the processed/compressed signal.

Parallel compression is when you set up a separate bus for the compression and you blend in the compressed signal with the original uncompressed signal.

If you were doing this in a software DAW, serial compression would be with the compressor plug-in put into a channel insert.  Parallel compression would be setting the compressor up on an FX bus or group channel (or whatever your DAW calls it) and using FX sends (or duplicate tracks routed to the group track with the compressor) to control how much of the signal you want sent to the compressor, along with the volume of the compressor channel, to control the blend of the compressed signal with the uncompressed signal.

Some compressors now have "mix" controls on them which basically allow you to do more simple parallel compression by putting the compressor on the insert and then using the "mix" control to determine the balance between compressed and uncompressed signal.  Some DAW software, such as Reaper, also have "mix" controls on each plugin panel window, also allowing you to do parallel compression with just an insert.

As for when you would use each, in the majority of circumstances when you are using the compressor mostly to control the dynamics of a track, you would use it in a serial setup on a channel insert, so that you are only hearing the compressed signal in the mix.

Parallel compression is used more for an effect.  Typically you would set up the compressor to do some extreme compression so you are hearing artifacts or distortion from the compressor, and you blend that in to taste with the original signal to add a touch of that "color" to the signal.  However, you can also use parallel compression and compress fairly heavily, but without causing distortion, and just add some of that in with the original signal to kind of smooth it out a bit, but still retain some of the uncompressed signal as well.

Thanks for the reply.

I've read somewhere about how compression is used in such a "signature way" that experienced ears can tell if the song/music were recorded on the East Coast vs the West Coast vs London vs Nashville.

I'm curious as to why country music has such a different sound to it, the recording I mean, not the genre, and whether it's a difference in their approach to recording or the use of the compressor.

It "sounds to me" as if the bottom end is very "round" and punchy/dynamic - that is the best word I can think of -and with a very pronounced high end.

In your opinion, would this difference be attributable to a concerted effort to stay within certain accepted sound parameters that appeal to its audience, or would it be that those in that particular industry listen to each other and develop a "gang mentality" as to where they are going, or is it something driven by the record labels?

Of course this would apply across all genres probably if it actually applies in country music and may be the same type of pressure that exists in any industry.

But if this is the case, where does it leave the independent, maverick engineer who does things differently?

In re-reading my post, I see that I actually address 2 topics.

Your thoughts would be appreciated.

I think this goes back to your other posts about compression.  I don't think it's so much about compression as it is simply different styles of mixing for different styles of music, that has gradually evolved and changed over time.

There was certainly a time where there was a noticeable difference in mixing styles between east coast and west coast, but that was more in hip-hop music and it was more of an overall production style and sound than it was about compression.  One style was more dirty and raw sounding, and the other was more clean and more of a high-end "produced" sound.  But, over the years, those styles have merged together and there isn't so much distinction any more.

Again, I wouldn't pin it on compression, as I personally can't listen to an album these days and pick out the type of compression they used or in what location it was mixed.  Pretty much everything is over compressed and limited these days... so, it all starts sounding the same to me... just loud, bright, and harsh.

My personal opinion is that Country Music has always been about 10 years behind that of pop/rock music when it comes to sounds and mixing and such.  They have always been a bit more conservative, and more focused on the song and songwriting, than on image and style.  But, again, I think they are just a little bit behind the pop/rock scene and if you look at country music over the years, it certainly has been catching up and sounds quite a bit like pop/rock music of just a few years back, but with some fiddles and pedal steel guitars thrown in!

But, I personally don't listen to a whole lot of country music, so don't take what I say for gospel.  I usually just hear the stuff that has crossed over into pop/rock radio.

Another factor is that many of the top hit songs that you hear in any style are mixed by only a handful of superstar mixing engineers, so that could contribute to certain styles having a certain sound to them, since it's often the same guy mixing a lot of the hits.  Record labels tend to have a herd mentality and if someone has a big hit using a certain guy producing and mixing, other labels will hire the same team to try to duplicate that.

Add to that the fact that there are certainly trends in each style, and people like to follow those trends so as to not alienate the audience for that particular style.  So, people try to copy the sound of other hit songs in the style they are working in.  At least to some extent.  There are always those who will try to push the envelope to push the styles forward in a new direction... sometimes it works, and sometimes it doesn't.  But, certainly the sound of mixes in all styles has gradually evolved and changed over the years.  Again, I don't think it comes down to compression as the single culprit, as compressors have changed very little over the years.  It's more of a general recording, producing, and mixing style thing that has changed with the trends/style.

Personally, I prefer music that defies the current trends and has a timeless quality to it, where the production and recording/mixing style are only there to serve the song and not trying to mold the song into what is currently trendy.  There is plenty of great music out there recorded, produced, and mixed in such a way that it will still be relevant no matter when in time it is played.  Lots of classic pop and rock songs (and I'm sure country and other styles as well) are like this... they still sound great today even though they were recorded quite a while ago.

That's what I personally try to do.  I don't try to match current trends when I mix.  Instead, I listen to the song and the music and try to serve the song the best that I can.  I don't throw in lots of gimmicks or over process something just because it's trendy.  I do what the song tells me it needs, and try to stay out of the way of the song so that the listener is ONLY hearing the song and and music and NOT the mix or production techniques (unless they are a recording geek like me and specifically listening for that stuff).  Of course, I still listen to music and am influenced by current music and trends, so I'm not going to throw big 80s style reverb and delays all over everything unless something in the song really calls for it.

Also, I feel that compression should NOT be heard, unless you are using it for a special effect.  If you can hear a compressor working, you set it up wrong (unless, again, you purposely did it for effect).  That's why I keep coming back to saying that I don't believe all these differences you are hearing and asking about are simply about the use of compression.  Certainly compression is overused these days, as that seems to be the current trend in every style, but the good engineers still strive to make the compression serve the music rather than have it be heard as a sound of its own.

I still believe that the general over compression and limiting of music these days is more to do with the demands of the record labels and artists who are still caught up in the "louder is better" mentality of the loudness wars.  It has affected all styles of music, including country music and even jazz.  I'm hoping this is a passing fad.

However, the punchy bottom end bass thing is more of a style thing than it is about compression.  Some people just mix the bass more up front and prominent than others.  Also, my belief is country music is still more about the song and lyrics than it is about being overly produced and trendy, so in that style a lot of the backing instruments will be mixed a bit lower to keep the vocals more out front, so there will be a bit more room for the foundation instruments (drums and bass) to cut through since the other instruments are not as up front.  When there is more space like that, the bass can be made to sound more full without the mix becoming too muddy.  Whereas in heavy metal and rock type music where there is a loud wall of guitars, the bass simply doesn't have as much room to be heard in the mix, and so it will be EQ'd differently to cut through that wall of guitars (if you make the bass big and full on its own in metal music, it will sound like mud when you put the guitars in the mix.... so, usually you take a lot of the low end out of the bass in that style, and add a lot of the upper harmonics).

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