In the era of "loudness war", a modern popular music song with no quiet passages generally has a flat dynamic range:

dynamic range

Clipping is also common - albums can be practically 100% distorted when record producers strive for maximal volume.

As acoustic music relies on shifts in dynamics, is dynamic range compression used by recording engineers in classical music recordings?

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    This may be better suited for the Sound Design SE. I'm not an engineer or Classical musician but from my experience, I would guess that they do use compressors just not as drastically. Classical music is probably the most dynamic, with drastic high/low volumes, so that needs to be represented in the final product, however, the music needs to be listenable in more than just a perfect setting, like in a car, so the quiet stuff needs to come up a bit. I imagine there are some tricks to being able to get the low dynamics easily heard without taking away from the loud moments. – Basstickler Sep 25 '17 at 20:17
  • Term for "quiet passages"? "Interlude"? – user598527 Sep 25 '17 at 20:45
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    I don't think that an interlude is explicitly quiet, though it is usually not incredibly loud, but I can say for sure that not all quiet passages would be considered interludes. If you look at modern Classical, basically anything from 20th century onward, the traditional forms became less common, so formal interludes are not necessarily even found. – Basstickler Sep 25 '17 at 20:48
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    Compression might be used to a relatively small degree, but in the UK it's interesting to compare two "classical music" radio channels: BBC Radio 3 is often jokingly called "the quiet one" because their "normal" broadcasting level is -10dB below the peak signal level so that peaks in live broadcasts don't distort with no compression. Compare with the commercial station "Classic FM" which is aimed in part at listeners who are driving, and is notorious for compressing all the life out of classical recorded music when it broadcasts it - and their adverts are all compressed to the limit, of course – user19146 Sep 26 '17 at 0:36
  • ... incidentally, Radio 3 are now experimenting with streaming 24-bit audio over their internet radio channel rather than 16-bit when broadcasting live performances, to maintain high quality at the lower signal levels. They are happy to broadcast long "quiet" passages of music at levels around -40 to -45 dB, and if anyone really wants to listen to that in their car, they can buy their own compressor! – user19146 Sep 26 '17 at 0:38

Yes, compression is used in classical recording, but not as heavily as in rock, and not as a weapon in 'loudness wars'. Not everyone listens in a perfectly quiet environment, on high quality equipment. A little compression, to bring the softest content up a bit, can be the lesser of two evils. There was controversy recently when BBC Radio 3 took to compressing their output a little more during the 'drivetime' slots. Purists listening on their home audiophile systems lost a bit of quality. The notable audience sector listing in their cars on the way to/from work could at least HEAR the soft flute solos!

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It depends on how classical music is recorded. If it is recorded mainly with two aerial microphones, it does not need much compression, but if it is recorded with many microphones very close to the instruments, it is necessary to compress each microphone, each channel, separately. Failure to do so would be like listening by placing the ear 1 or 1 1/2 meters away from each instrument. Nobody could stand it. There are even musicians who get angry when you put a compressor on a channel, but they do not realize that one listens to the instruments, the orchestra, 20, 30,.. or 60 meters far away. And air is a natural compressor.

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    “Air is a natural compressor” is pretty much nonsense. At any sound-level achievable with acoustic instruments, air responds to an excellent approximation linearly. Even hundreds of metres from the source, the sound won't be measurably compressed, certainly not audibly. — What the room effects you get with ærial microphones do change, obviously, is the transient shape and to some degree frequency response. That is the reason such a recording is easier on the ears: it contains, in particular, less jarring high-frequency transients. But this is by itself completely unrelated to compression. – leftaroundabout Oct 12 '17 at 13:17
  • ...that said: if you set up lots of mics and put individual compressors on each, this also makes the recording more reverb-ey because whenever instrument A plays loudly, the balance of its signal will shift away from that instrument's own mic, towards the other mics which don't pick up much of A directly, but do pick up additional ambience, i.e. add reverb to A. But again, that's not really directly a compressor effect, just a consequence of the mixing of many mics. – leftaroundabout Oct 12 '17 at 13:21
  • BTW welcome to Music.SE. This is actually a reasonably nice answer, just with details that aren't physically correct. – leftaroundabout Oct 12 '17 at 13:24
  • Sorry. This answer is not correct. This is not the way to record classical music. It is extremely rare to have a compressor on the close mics when recording classical. It may be used in a stage setting, but not in recording. The term aerial microphones is never used by recording engineers either. – ghellquist Nov 29 '17 at 6:58

As acoustic music relies on shifts in dynamics, is dynamic range compression used by recording engineers in classical music recordings?

Yes, although there is a school of using only two microphones and no processing. Generally, for records and TV music the dynamic range is reduced. It is of course dependant on the material, but if you look at symphonic works they often have a dynamic range much larger that a typical listener, equipment and surroundings can accommodate.

It is done, at least in the recordings I have done and the ones I have been involved in, more by "riding the faders" than by using a compressor. It might be that there are better compressors available, but the ones I have tested tend to give an unwanted signature modification of the sound. A limiter might be useful to contain some of the very strong accents, say that extra strong bass drum beat at the end of a symphony. In a DAW I instead use volume automation. The low pitched lyrical section will get a bit of volume boost, the fortissimo section will get a bit of volume decrease. How much to boost or decrease is all about taste. If using several microphones, a recording session today may use 50 or more microphones, you will probably raise an instrument mic slightly when playing a solo and turn it lower otherwise. This as well tends to reduce dynamic range.

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