The metronome. It introduces us to the concept of keeping time, helping us find stability within it. However, this time is essentially artificial, mechanical. It is planned out to land on certain parts of a second at a certain time. This of course is very helpful because a metronome can show you various combinations of those beats per minute and its use for this purpose is extremely important. But, when we take away the metronome, what do we rely on? What can we relate our time to? I think that, ultimately, time is felt. 120bpms feels a certain way and 121bpms feels a certain way. I think of time more like I do tuning. With tuning, usually the darker the sound I want, the tendency is to play it "flatter"; the brighter I want the sound, the "sharper" I'll play it. Similarly, if you were to tune a major chord, you cannot simply play every note in tune with themselves and put the 3 together. They have to be tuned in relation to each other. The spaces, intervals, between the notes can't be too large or the chord sounds too wide, and vice versa. I compare this way of tuning to my way of setting and keeping time.
The space between notes is comprised of the appearance or disappearance of intervals and silence. With time, the space the silence takes up creates the tempo. How do you count 30bpm? A trick is to just think 60bpm and play every other beat. The downside is, you're still not playing 30bpm. You're playing 60bpm at 30bpm, so the character of the 30bpm ends up feeling like 60bpm. Unless you can feel that space between each quarter, you can't play the character of that tempo or any of its subdivisions. It's really obvious to hear with slow tempos, but not so obvious with fast ones. When you play 165bpm, yes it's fast but it's not hurried. It's slower than you think. Unless you can feel the quarter without the subdivisions, trying to make it to the next beat instead of landing on it, it will sound "notey", as if it's just played note to note individually, unconnected. Feel the bigger beat and don't use the subdivisions as a crutch.
The idea is not to do away with subdivisions, but to make sure the subdivisions are taken from the desired tempo and not an extract of another one, put into an equation and processed to equal the desired tempo. The big beat is king. Now, when the beat is found, you have 3 main choices: play right on, ahead or behind (perfectly in tune, a little sharp, a little flat). The key to this is to have control and flexibility over these changes. You should know when you drag, rush or are "perfect" and a metronome is great for experimenting with that. After that, the choices, with individual notes within the beat, are their lengths. You can play the eighth note its full value, longer or shorter. This too can give allusions and characters within the time itself. My instructors at DePaul, Marc Damoulakis and Eric Millstein, gave me a perfect combination when it came to this way of thinking.
With Eric, he always talked about the character of pieces, each having a certain sound, a certain groove and feel. Marc always talked about the lengths, colors and feel of the notes, having complete control and endless varieties of them (both of course had similar views on all topics). Put these two together and you get a more musical interpretation of not only the music itself, but time as a whole. So a march tempo with long but bright notes sounds more stately, but change the bright to dark and it sounds tyrannical. You could change the drum or the tempo to do either, but why bother when you can just use your hands?
When in the orchestra, you have to be flexible. This takes a little time to get used, but the more music you listen to, the faster you'll figure it out. Notes before and after pauses or holds, long or short (but especially long), ritardandos and accelerandos are the ones that are most important to pick up as soon as possible. Each metric transition has common tendencies that almost every orchestra is sure to do. It's something you have to hear, feel, react to and not rush into or hesitate with. When in doubt, watch the concert master, or whomever is the main voice at the time, but when you can react without the aide of outside forces, then you are in the moment, and ultimately, on the stage, that's what you should be getting into anyway. Time is now, living moment to moment.
Listening is important to your time. Playing with a human being means you have to be flexible, even when you are being rigid with the time. If you are playing a march and people begin to drag, it's better to play a darker (behind) version to try to get the tempo back instead of blazing away or staying in the center of beat (this is only if you are the only one with the rhythmic figure, otherwise do stick as close to the majority as possible without losing the desired time. I find the slight behind or ahead placement is good to stay with the group and not lose them or the time). Of course things like this cannot be mechanically calculated in the moment because it can change note to note. Your ears, your feel and your reflexes have to be open to change and adapt moment to moment, note to note, especially on pieces that come with these tendencies to rush or drag.
So practice with a metronome, get acquainted with the time as often as possible, and when you're on stage throw it away. Mechanics have no place in the performance. No one wants to hear a string player's string crossings while they are playing a beautiful phrase. It would sound like someone saying, "I.......................love.........................................you." No one will say, "Oh the orchestra was dragging, but that snare drummer just kept going. Way to stay in time!" No, they would say, "He should've went with the orchestra or something." So of course, get the technique, get the stability of time within yourself, but when it's time to perform that particular piece on that particular night before or after a particular piece that you either play on or not, 60bpms might not sound like 60bpms that day. It might feel like 61bpms. What does the moment say it feels like, what does the moment say it sounds like, what's the time and tempo in that moment. As you practice, if you drag you will notice it because you will feel yourself slipping away from the moment, or if you rush you will feel yourself falling forward. You won't need to always depend on the recording's playback; you should be able to tell right then and there what happened to your time! When you're aware of those ideas and atmospheric changes, first in practice and then in performance, then you'll really be playing in time.