(Ed note: You'll hear the phrase 'learn to trust your ears' often on this site. We firmly believe it's important to properly train your ears and then trust them while doing digital recording. Let's start with Mac's thoughts on the subject.)
There seems to be some difficulty in understanding what it means to train the human ear (and the brain between) and how subjective or objective the use of same may be. Let me start by stating this in no uncertain terms: Your ears are simply superb instruments for judging audio events. And for good reason when you think about it: Everything you do in the studio has but one purpose and one purpose only, to tantalize and delight the human ear at playback. Anything else just has to do with the methodology for getting to that one point.
There are a few different facets to ear training, so let's dive right in and identify them...
For a musician, the ability to hear the differences in musical intervals, that which we call "Relative Pitch", is a very desirable if not mandatory skill to practice and develop. Practicing identifying the basic twelve musical intervals within the octave, moving both up and down, will improve your ability to hear any musical event by many orders of magnitude. Contrary to what some may believe, a well-practiced ear at Relative Pitch intervals can simply listen to a song or an entire orchestration for that matter and realize with perfect infallibility what all the note relationships are. Key signature does not matter. What's important are the number of half steps between notes. That's a very powerful instrument to have, and best of all, you already have everything needed to start using it, all you have to do now is spend some time internalizing each of the twelve intervals in upward and downward motion, and practice identifying them. There are proggies designed to help you with this that work like a PC game, no excuses for not getting with the program.
Then there is the so-called "Perfect Pitch", which is something that may get in the way of identifying Relative Intervals if the target instruments are not dead in tune or tempered. Perfect Pitch (Absolute Pitch is a better term) can actually be detrimental to one's ability to play an instrument, old wives tales notwithstanding. A recording engineer does not need Absolute Pitch abilities to get by, one can simply compare keyboard or guitar notes to certain unknown frequencies to ballpark them from the note to the frequency domain with the help of a frequency chart anyway. Most still believe Absolute Pitch abilities to be some sort of talent or gift, but the facts are that you can once again train your ear to deal with this sort of pitch recognition if that is your goal, David Burge has been selling the course for years, but remember what I said earlier about Perfect Pitch, I have known musicians who have wanted to get it removed because it gets in their way.
Now let's talk about training our ears to know what sounds good and right with electronically reproduced music and such...
Just as with the Interval and Pitch recognition exercises, no amount of writing or reading is going to develop the Golden Ears for you. What will do it for you is making sure that what you listen to and how you listen to it is correct, and the rest is up to you and the time you spend working at it daily. First is your listening system; the equipment. One does not need to spend a bunch of money here, but one does need to have the basics plus the basic knowledge of how to use it in order to be able to hear things correctly. I like two-way speakers over multiple drivers, a good medium to high quality stereo amp or receiver, and a good listening environment, set up properly.
Place the stereo speakers at ear height to your favorite listening chair, and whatever the room dimensions, place the speakers and chair in a pretty exact equilateral triangle to suit. Sit there and listen to your CDs and such right in the middle of the stereo field like that.
So how do we set the tone controls and such? The Fletcher Munson curve really shows us that our ears hear midrange area much better than they hear the extremes of bass and treble. So that 'Loudness' button on the stereo really has a good purpose: When listening at low to medium volume levels, kick the loudness button in. What the Loudness button really does is imply a 'Smiley Face' EQ curve such that the lows and highs are boosted a bit, and the midrange is cut a bit. This is not flat, but because of the way the human ear works, it will end up as being recognized as flat response in your brain, and that is what the whole thing is about; at low to medium volumes anyway. There has been so much hype about the need for flat response that it makes me want to puke, it just isn't so. Actually a totally flat response system will be detrimental to your purpose here, which is to hear what the recording engineer and especially the mastering engineer INTENDED for you to hear. Fletcher Munson is real; which is why the engineers that designed that stereo went to all the trouble to place a properly designed Loudness Contour circuit with the switch on the front panel of all those stereos, man. Tone controls start at 12 o'clock, don't be surprised if tweaking both over towards 1 o'clock position doesn't sound a bit richer and that's perfectly alright. Avoid extreme positions on tone controls, however, that will over color an area and your ears will not be training to hear the recordings as intended.
As volume goes up, loudness curve should diminish. Most all of the modern stereos are set up such that you should turn the loudness button to off when the big volume knob approaches the 12 o'clock position or perhaps 11 o'clock depending upon your speaker efficiencies. Turning the big volume knob past 1 o'clock is usually a bad thing and a useless endeavor as headroom will surely suffer and you won't be hearing what the recording engineer intended for you to hear at that point. You may also blow your speaker drivers, but what's worse is that you are going to blow your ears, and last I checked nobody was selling replacement parts for the human ear. So keep the volumes at reasonable levels if you want to train your ears.
I hate headphones for serious stereo music listening. I have my reasons, just let it be said that if you do a whole lot of listening via headphones you are not training your ears to get to that point where you can trust them to be infallible when seated in front of the studio monitors.
As with playing the guitar, or any other instrument for that matter, mastering your own ears takes time, and grows a little bit each day if you put the time into it. Sorry, but I know of no instant method.
The above stuff is basic, intended to get those who may not have all the facts into the starting gate. Try it before you knock it. These things have always stood me in good stead.
(Ed note: Ok, so how to train your ears? Here's a post by Pete with some great advice.)
Since the discussion that arose from my request about vocal training information, I've found a few REALLY neat free programs out there for ear training. The first of these is called Solfege. Solfege is a GNU/GPL program, which means it is open-source. It is available for all operating systems. This program provides comprehensive melodic and harmonic interval, chord recognition including inversion and toptone, general chord recognition, interval voice, modal recognition, chord alteration recognition, melodic transcription, melodic voice, harmonic interval transcription, relative interval size recognition, vocal harmony, rhythmic notation, beats per minute, and harmonic transcription training. In other words... WOW!
Two others I really like are Functional Ear Trainer and Functional Ear Trainer Advanced. The Functional Ear Trainer teaches the ability to recognize notes against a given key, and can be configured by preset for chord intervals, partial major scales, full major scales, full chromatic or user's choice of notes, in any major, minor, harmonic or melodic key. The key is established by your choice of I-IV-V-I, ii-V-I, I only, root note only or none.
Functional Ear Trainer Advanced is another interval trainer, which can be configured for fixed key or random key, fixed key type or random key type, tempo, random note duration, and ascending, descending and harmonic intervals, fixed, random or no key reference. Both Functional Ear Trainers are available for Windows at http://www.miles.be.
Another one I use and love (but hadn't though about in terms of voice training, which is where all of that came from,) is Simple Feedback Trainer, which trains the ear to recognize specific frequency bands. After reviewing demos of many commercial and GPL programs for ear training, these stood out for me in all categories. Enjoy...
Way to go, Pete.
Be sure to not let all the options get in your way: start with the simplest interval trainer at a fixed pitch and don't try to go any further until you can nail all the intervals that way. Remember, it's the RELATIVE pitch recognition that will do the most for your music skills. For some people that only takes ten to twenty minutes a day for a couple of weeks. Others may find it takes longer, no sweat just keep at it.
Just being able to identify all twelve intervals up and all twelve intervals moving down inside the octave will improve one's playing and singing tremendously. The neat thing about studies such as these are that once you "get" them, you have them for the rest of your life.