I have a hypothesis that there are a few global tempos that everyone feels more accurately than others, perhaps due to the nature of old school metronomes not providing such precision as digital metronomes, and up until the 80s or 90s the canon of western music had all been composed at these…so naturally we are more inclined to classical adagio, andante, moderato, allegro, presto, etc.
Of course we all have those tempos in which we feel comfortable as players, and I think for a lot of us it is right around 100bpm, perhaps even up to 120bpm, which is supposedly close to a rhythm in sync with our resting heart rates. All that being said, I discovered one day that it was easier for me to play 120bpm than 117bpm as I kept either rushing or dragging at the lower tempo…I think because it is in this grey area between 112 and 120. Although, if we’re talking psychology, maybe I just convinced myself of this phenomenon and was then able to play the faster tempo thanks to some sort of placebo effect. So perhaps a good way to set your metronome is using those global markings, rather than finding yourself in an odd spot thanks to 1bpm increases.
But with this idea of our psychological fixation on certain tempos, if you’re practicing using an increasing tempo, it’s easier to notice a 5bpm increase than a 2bpm increase, so it’s very likely that if you were able to play well at 112, but not at 114 it’s because you’re not feeling the rhythm properly or you’re still hearing 112. Similarly it’s likely that if you hear the tempo jump up from 115 to 120, it may sound like a huge increase and create stress, so maybe you want to pause the metronome, even take a water break and then set it to the next interval before you start it clicking again. Or maybe using the smaller increases can help you feel less anxiety as the tempo builds, and therefore you maintain more control throughout the practice.
I’ve also noticed that if I approach a tempo cold (without any gradual increase) it can sound much slower and less stressful and is far easier to play than if I set my metronome to gradually approach it. And playing anything unfamiliar can make even 60 bpm sound too fast.
Lastly, for some great insights into all of this, check out the book, This is Your Brain on Music