Playing in Precise Time
A student recently commented on the challenges of tapping his feet in time and the difficulties of playing in precise time playing with a metronome. You might also benefit from my response...
"When you truly know a song... fully internalized it... not thinking, but in what's called the "flow state"... you can tap your foot in time. I use my foot as a canary in the coal mine... if it stalls or stops... it's a sign that I haven't fully internalized that passage of a song yet, and to practice I go. The same goes with a metronome. In our case of solo harmonica playing, the audience will tap their feet to what you're playing... swaying their bodies... and they won't be able to do this if your internal timing (trained by using a metronome) is not good. You could be speeding up, slowing down or dropping beats, and without the imperial reference of a metronome in your practice, you wouldn't know this (recording yourself and tapping your feet along to your recording is also a great way to check this).
Also, if the audience claps their hands, THEY are now the metronome. I would prefer that you say to yourself, "Cool, they're getting into what I'm playing... we're groovin' together!" and not, "Oh crap, they're clapping their hands, I hope I can stay in time!"
Another area where precise timing is valuable is when playing breaks in a song (where the band stops, but you continue to play in time). Our most common break is that of an ending. After signaling for an ending, you're all by yourself. When you signal a break for the I Chord (one chord) in the beginning of the form, the band will meet you four bars later on the IV Chord. Your ability to have rock-solid time in both these situations is paramount for the band to be able to follow you and come back in with confidence.
I hope some of these points give you some clarity on why we learn how to play in precise time."