The phrase 'playing in the pocket' is used sometimes, in jazz, hip hop, funk etc. It sometimes refers to the way a drummer plays, sometimes to how an ensemble works together. I've Googled the term, and can't find a good, clear explanation of what it actually is. May be the good time-keeping, may be phrasing. It's one of those things that, when it's happening, you know you're playing 'in the pocket'. But exactly WHAT is it that happens?
You're on the right track. It's actually a combination of some of the elements that you've mentioned. If the band is not playing together, then they won't be "in the pocket", this much is clear. It goes a bit deeper than just simply staying together and playing at the same tempo. It can also be song-based, meaning it's dependent on the tempo of the song. Let's say that the most comfortable tempo for Song A is 70BPM, but the band is playing at around 63BPM. The song will feel like it's dragging and that sensation of "playing in the pocket" will not be achieved even if the band is perfectly together!
To add to your point about playing together, the bass player and drummer really need to work together, especially in more syncopated songs, to achieve rhythms that match. This is not an absolute rule, but the rhythm of the bass and bass drum tend to match.
You may be familiar with the concepts of semiotics, where words have meanings that have nothing to do with their supposed dictionary definitions, and have everything to do with signifying that the user of the term is part of an identifiable group.
People who use the phrase "in the pocket" knowledgably are usually communicating understanding of a particular sensation that skilled (and lucky) musicians get to experience when they are working successfully as a group.
So the sequence could be:
You hear a group. In your judgment they are really happening. You are moved emotionally and rhythmically. You likely will note some of the technical aspects of playing together that the other answers list.
On the spot or later you describe what you hear in this band to someone as "in the pocket."
First question: Is the person you are talking to familiar with the term? If not, you may find yourself trying to explain.
A person who knows the term and who is there with you will compare his or her perception of the performance with yours. Depending on that person's expertise you will either gain, maintain or lose status with that person when it comes to evaluating whether or not a performance is "in the pocket." A healthy debate might ensue, or you may be patronized, depending on how that person feels about you, and the level of mutual respect that is operating.
If you are relating this experience to someone afterward, your history and credibility will come into play. If your credibility is well established, your use of the phrase will act as a recommendation - this band is an experience you should seek out. If not, not.
So I believe the phrase is most useful as a means for musicians and others in the know to trade insights that don't depend on technical definitions, but exist more in the realm of feeling and sensing.
Of course, it would be very rare for a group playing out of tune and/or out of time to ever be so described, but every person in the know can tell you that to "play in the pocket" is something far beyond the basics. It is a lot like love - easy to say, very difficult to describe and define without squeezing the life out of it. But when someone says "I love you," depending on who it is, you know what to do about it.
In The Jazz Theory Book, Mark Levine defines playing in the pocket simply as grooving, where the rhythm section is locked in and working as a unit.
in the pocket When the music is rhythmically in a groove.
groove The “lock” between members of a rhythm section playing well together.
TL;DR Leaving few details out, I'd define it as multiple overlapping swings with beat/accents that all instruments lock into (rhythm-responsible instruments should keep sync most frequently & accurately). The overall feel can be varied by offsetting each instruments timing (playing bit ahead the 'beat/accent' or behind). In improvisation if other players perceive a feel change and then change what they do it can cause a chaos as everyone adjusts what they do - perhaps one player changed feel for syncopation-like effect - if everyone in band changes in response the desired effect falls apart. Some coordination/agreement/leading is thus needed for improvisation if one likes doing such tricks.
Found this recent book because it referred a paper where academics clearly had recognized one part of the "pocket". (it's not just "band playing in sync". You can get things play in sync in a computer sequencer and it won't be the pocket that people in know talk about - in my dictionary pocket is something that gets atleast some people (*NFP is probably "dancer personality") moving to the music. Otherwise you could say all electronic music is "in the pocket" - I used to do electronic music and to get the pocket I had to find optimal tempo and adjust swings and shuffles for drums first and then play to those)
This is the paper. http://www.speech.kth.se/prod/publications/files/822.pdf
It focuses on adjustment that musically talented players do to their swing in relation to large changes in tempo. One explanation for this is that as the tempo changes enough, the time slice in which invidual note timing swings (shifts around a midpoint) changes in length. Instruments (ADSR) envelope may not be easily changeable (without effects rack) causing the need to adjust your playing so the feel of the swing remains noticeable.
The drums (how long their sound sustains) or whatever rhythm instrument that is most in focus determines the optimal tempo through the notes envelope and overlap. Faster tempo requires reducing sustain/release time, faster attacks in order to avoid the sounds getting so overlapped that the feel is lost.
Swing (this is what creates the "feel" or urge to dance, the "pocket" is when all players are able to play around the swing - all feeling the swing) :
Study of some computer-tracked songs that clearly groove highlighted that the song under study didn't actually have an instrument based swing parameter. Instead the composer was rapidly alternating entire project between two tempos.
After lot of listening I conclude that the most skilled compositions may actually have multiple simultaneous swings of different frequency.
1) "dialogue" - compose the track in a manner where a variation of same theme is played twice with some modifications (vary the arpeggio, instrument etc) - in particular, tempo. So part of the song is in a different tempo. Typical in classical music. This won't create a pocket, just a "dialogue" between instruments. Perhaps one part/instrument is upbeat and then followed by another more slower and melancholic feel.
2) traditional easy to play swing: When you have your optimal tempo figured out, don't play at that tempo but actually play at say -2% and +2% BPM around it, smoothly alternating the tempo between each half interval (8 beats).
3) dance music swing: have the notes swing also (achieved eg. by the rapid tempo variation explained or instrument specific swing parameter)
All of this maybe achieved in electronic music by LFO's and clock dividers as seen here (see 11m20s - 12m00s):
Is 3) actually called a shuffle? IMO shuffle is a combination of #2 interval swing and #3 note-swing, accents + ghost notes. That's atleast what I hear going on if I listen to the best of the best (search "Jeff Porcano instructional" in youtube) when they demonstrate shuffle on drums. You could say shuffle is just part of that but then you'd not have the feel needed for pocket.
To get single instrument to really sound 'talented' you also need to play some notes legato, vary velocity, tweak sustain/release, accents while doing those alternations in tempo and swinging the notes.
If there is some genetic talent involved in swing, it's IMHO about the ability to listen to music and if you can't resist nodding your head, tapping your feet etc, then you have that genetic talent. To turn it to playing or composition skill, you also need trait of perfectionism - this allows noticing what sounds like a bad mistake and what sounds like good mistake worth pursuing. The happy accidents I do always are like "wow!" and then I'm sad when I can't repeat it immediately but have to practise a particular riff for 1-4 hours to get it just like the accident was. The more experience the shorter this practise time becomes. But since we are talking about some millisecond differences between perfect and not perfect in terms of how I feel the timing, that's why it takes lot of practise.
I leave you with a song for testing whether you have the (what I assume to be) genetic trait of feeling the pocket. I am very sensitive to "perfect pocket" so if the timing is even a little bit off then I don't start dancing to it but rather I start frowning or mute/switch song. That's the perfectionism talking that allowed me to simply through introspective feeling to reverse engineer what elements make up professional playing.
Same song, same player, both groove but one of these is more perfect in pocket-terms than other. In the spoiler below I speculate why I think the player decided to remove the other performance from their channel. (it's re-up by someone else)
it's the second link that's more in pocket - the first one has lots of notes played late. Maybe by couple milliseconds on average. It's likely the player felt a more laidback feel suited the song but as that is extremely difficult to achieve in such busy song didn't quite get it as perfectly as the more "tighter" version in 2nd link - to get it not only you have to perfectly delay the attack but also modify the envelope of the sound because if you don't, it will sound like the notes get cut prematurely. This time between the note cutting and next note starting gets shorter with faster tempo so as that happens, using some sound processing effects can help in achieving the feel desired.
EDIT: Very interesting note about the video, I noticed the player loses the pocket (sounds like computer sequencer/mediocre player) when (s)he stops dancing around the beat. I have noticed this phenomenom myself too, if I am rigid I lose track of the #2 swing more easily and in order to do note-swing I also have to use my mouth to spell (silent vocalization of the notes) out the timing envelopes to get that millisecond timing right. I learned this technique from youtube video talking about how jazz players train.
Example of how effects processors can be used to modify the feel in significant way:
Here's the Jeff Porcano video mentioned. It goes into specifics of the note level swing & shuffle.
I think "in the pocket" typically refers to a groove where the snare drum (on 2 & 4) is ever so slightly late (milliseconds), meanwhile everything else is tight and grooving without slowing down.
edit - possibly mistaken, in the pocket might describe a snare that's exact on time.
edit2 - this one supports the idea of the "pocket"being slightly behind the beat http://www.pearldrummersforum.com/showthread.php?114439-Defining-the-quot-Pocket-quot
I've wondered about this term for a long time. I've also asked fellow musicians about its meaning ... and these are people who actually use the term ... and they haven't been able to define it. Ha.
That being said, here's my take on it: the term "playing in the pocket" is not usually used for the whole band. If fact, in my experience, it usually refers to one band member only -- the bass player.
So what's the "pocket"? I believe the "pocket" is the illusion of "time slices" which the drummer creates. It could refer to a whole measure, but also to a sub-count of a measure. For example, the time slice between drum hits is a "pocket". But also, for a typical drummer who basically repeats one measure over and over, the "pocket" could be a whole measure.
So when a bass player is "playing in the pocket", he is doing the following:
1.) He's timing the striking of his notes so that they coincide with the hits that drummer is pounding out. That does not necessarily mean that they are in-sync, note-for-note with hit-for-hit. This is where "artistry" comes to play. Typically the drummer "leads" the rhythm section. He autonomously chooses whether to hit this drum or that drum at every given instant in time. The bass player typically follows the drummer and attempts to "flow into" what the drummer is doing as well as to accentuate certain areas. This does not mean that the bass player is a less-important role. Not at all. But someone has to be the "lead", and that's typically the drummer.
2.) He's choosing the note which he will play (i.e. the frequency) based upon the chord changes that the guitar and/or keyboard is playing. For any given chord, there are numerous bass notes which will "work" well. The bass player, as part of the task of "playing in the pocket" must also be basically in-sync with the keys and/or guitar so that the frequency that the bass is playing is compatible with the chord at that moment. Note that in simplistic terms, this would mean that the bass player would play the root of the chord on the downbeat of the measure. This is typical for rock and roll. But jazz certainly takes huge liberties to do otherwise. Ha.
So "playing in the pocket" is really the job-description of a bass player - only. He needs to adjust his timing and his choice of notes so as to properly interface with the other instruments in the band.
But again, let it be known that by no means do all bands even want the bass player to "play in the pocket". That is a style, really. I like it. It's straightforward. It definitely tends to "groove" as others have said. It "feels good" to most people. But it's more like "popular" music. More esoteric music, like classical and jazz do not typically have the bass player "playing in the pocket".
I'm no musician but I believe its like "flowing" so to speak. I think it's like getting in the zone in some sort of improv moment or playing something out so spot on and synchronized that you ARE what you are playing, you don't feel the time passing by, you are not thinking about anything but what you are doing at that moment, self consciousness goes out the window along with anything else that is not THAT MOMENT.
When a rhythm section is playing in the pocket it ultimately means "groove" in any context. An example of a rhythm section that is ALWAYS "in the pocket" would be Pino Paladino and Steve Jordan playing ANYTHING together. It's tight, it flows, it grooves, it feels good, and it can be played without applying much thought and letting the vibe, groove, and feel of it all guide you.
Im sure "the pocket" could definitely be described in a technical way, but when I experience it on a stage or from a crowd its obvious...and the beautiful thing about it, is as a listener, you can feel it too. It makes you smile and think to yourself "Yeaaaaa, THERE it is." Playing in the pocket is all about rhythm and groove. The song stops feeling like a song and starts feeling like a broke-in La-Z-Boy for your ears.
A couple of additions from around the interwebs:
- A group playing in perfect time (locked in etc - per other definitions) plus attitude, or authority. Like watching Prince perform live: he was the absolute boss of the show.
- Important to note that pocket is specific to a particular groove, thus to a particular genre, not a "1 & 3" or other element of the beat. Bebop, hard rock, funk, bluegrass, all are different but all can have a pocket.