It can be discouraging when you love the feel of a particular performance but it somehow sounds a bit off; things aren’t as tight as they could be. A lot of times, that “offness” you’re hearing can be alleviated by editing the performance of the looser track(s) against another track that’s rhythmically where you want it to be, which we’ll call the “reference track.”
For example, let’s say you recorded a keyboard part that has all the soul that you want, but it doesn’t quite sound rhythmically tight with the bass track. Position the keyboard track in your DAW so that its waveform is right above or below the bass track’s waveform; the bass will be your reference track. Now look for where the transients (note attacks) from each track fall. Whenever you find that the transients of your keyboard track are off from your reference track, separate that note or passage from the rest of the audio clip (most DAWs have a “split” or “separate” command or tool that creates a new clip from the selected audio), adjust the timing of your keyboard note(s) by sliding it back and forth until it lines up with the appropriate bass note and sounds right “in the pocket” with the bass. Do this for the entire length of your track. Once you have the note or passage where you want it, be sure to add a very short fade-in/fade-out or crossfade to prevent clicks and pops in the audio playback.
Editing like this isn’t necessarily fun work; it can be time-consuming process depending on the length of the performance and how off from the reference track your track is. (However, you will get much faster with practice and experience.)
Using this type of “manual” rhythmic correction process will help your performance sound tight while preserving its natural feel. Because you’re adjusting the timing to match another live track, it will sound more natural than quantizing the part to a tempo grid.