Trading by price -- and "volume" -- requires a perceptual and conceptual readjustment that many people just can't make, and many of those who can make it don't want to. But making that adjustment is somewhat like parting a veil in that doing so enables one to look at the market in a very different way, one might say on a different level.
One must first accept the continuous nature of the market, the continuity of price, of transactions, of the trading activity that results in those transactions. The market exists independently of you and of whatever you're using to impose a conceptual structure. It exists independently of your charts and your indicators and your bars. It couldn't care less if you use candles or bars or plot this or that line or select a 5m bar interval or 8 or 23 or weekly or monthly or even use charts at all.
Therefore, trading by price and volume, or at least doing it well, requires getting past all that and perceiving price movement and the balance between buying pressure and selling pressure independently of the medium used to manifest or illlustrate or reveal the activity.
For example, the volume bar is a record of transactions, nothing more. The volume bar does not "mean" anything. It does not predict. It is not an indicator. Arriving at this particular destination seems to require travelling a tortuous route since so few are able to do it. But it's a large part of the perceptual and conceptual readjustment that I referred to earlier, i.e., one must see differently and one must create a different sense of what he sees, he must perceive differently and create a different structure based on those perceptions. As long as one believes, for example, that "big" volume must or at least should accompany "breakouts" and clings to this belief as ardently as he clings to his rosary beads or rabbit's foot or whatever, he will be unable to make this perceptual and conceptual shift.
If you can work your imagination and use it to travel in time, you will have a far easier time of this than most. Imagine, for example, a brokerage office at the turn of the 20th century. All you have to go by is transaction results -- prices paid -- on a tape. No charts. No price bars. No volume bars. You are then in a position wherein you must decide whether to buy or sell based on price action and your judgment of whether buying or selling pressures are dominant. You have to judge this balance by what's happening with price, e.g., how long it stays at a particular level, how often price pokes higher, how long it stays there, the frequency of these pokes, at what point they take hold and signal a climb, the extent of the pokes, whether or not they fail and when and where, etc., all of which is the result of the balance between buying and selling pressures and the continuous changes in dominance and degree of dominance.
One way of doing this using modern toys and tricks is to watch a Time and Sales window and nothing else after having turned off the bid and ask and volume. But this wouldn't do you any good unless you spent several hours at it and no one is going to do that. Another would be to plot a single bar for the day and watch it go up and down, but nobody's going to do that, either. Perhaps the least onerous exercise would be to follow a tick chart, set at one tick. Then follow it in real time. Not later, but real time. Granted this means a lot of screen time and only a handful of people are going to do it. But those few people are going to part that veil and understand the machinery at a very different level than most traders.
Once this is understood, the idea of wondering -- much less worrying -- about what a particular volume bar "means" is clearly ludicrous, as is the "meaning" of a particular price bar or "candle". If it is not understood, then the trader spends and wastes a great deal of time over "okay so this volume bar is higher than that volume bar but lower than this other volume bar, and price is going up (or down or nowhere), so...".