Many years ago, when I was at university, I remember being jealous of another student in my class who played flawlessly in tune. She never seemed to put a foot (or finger) wrong. I asked her how she did it, and she shrugged and said “I just got really addicted to playing in tune.”
I was a bit peeved at this response. I thought she might be superciliously implying that the rest of us were addicted to playing out of tune. I scowled and went back to my practice room.
Much later, it occurred to me that perhaps a lot of people are addicted to being out of tune, in the sense that they let poor intonation go unchecked in the practice room, glossing over it with big slides and vibrato, without really figuring out what good intonation is.
As I wrote in my book, this question is an absolute minefield. It depends hugely on whether other instruments are playing, and if so, which instruments. Sometimes we simply have no choice but to tune to the equally-tempered tuning of the piano, because the pianist physically can’t adjust to us. Sometimes we have to adjust to the woodwind and brass instruments in an orchestra or chamber ensemble, because they can’t hear us well enough to adjust to us. In a string quartet, we can use just intonation, but there are always cases where the intonation is negotiable and debatable.
When we’re playing solo, we can go with what makes the cello ring the most, and what makes our phrasing the most convincing. Barry Ross’s book A Violinist’s Guide to Exquisite Intonation, which proposes that our instruments will “tell” us what’s in tune and what’s not according to the properties of the harmonic series, changed my life. These days, I practise and teach a cello-adapted version of his principles.
After I read Ross’s astonishing work, I realized that I had become addicted to playing in tune! Nothing else satisfied me any more. If I couldn’t hear the cello making the optimal resonance that comes from a combination of really good intonation and really efficient bowstrokes, it bothered me hugely. I had to fix that thing, and ensure that I always played it in the way my cello “wanted” to be played.
It only took me 15 years to figure out what my classmate had known all along. Ah well, better late than never.