The topic of "deliberate practice" has been getting a fair amount of ink lately. Journalists whose beats range from business to the arts and many things in between have been filing stories that elucidate the substantial benefits of adherence to this discipline for those who aspire to real proficiency in any field of endeavor. (Read "On Musical Talent" by David Shenk.)
For example, if you hope to achieve competence in the sport of playing baseball you'd darn well better dedicate yourself to practice playing baseball. But whereas a general (non-deliberate) type of practice would serve to help those with a basic ability to run, field, and hit to achieve competency as a ballplayer, the theory is that it would take a different kind of practice to achieve real proficiency—a kind of practice structured around very specific elements of performance which, through conscious repetition and refinement, can be perfected (or nearly so) and, when combined with deliberate practice of all other important elements, create the blueprint for a virtuoso performance.
As an instrumentalist, I got exposed to the concept of deliberate practice from another instrumentalist (my father). But he didn't call it deliberate practice. He, like a lot of horn players of his generation, called it woodshedding —the identification of a particularly difficult and/or important passage of the music and the discipline to practice it repeatedly with specific goals in mind.
Most of the "shedding" I did was to improve my articulation through rapid passages of music, but dad was also a stickler for lots of long tones (to improve my consistency) and lots of playing pretty much everything at piano or pianissimo (to improve my control). I can't say it was fun, but it sure was rewarding at performance time.
Within the context of a chorus, it seems to me that there's a real need for deliberate practice on at least three levels—the individual, the section, and the chorus overall. Individuals need to woodshed the basics—notes, diction, rhythm, dynamics, navigation, etc.—to the point where they're in sync with the rest of their section. Sections need to woodshed cohesion, consistency, and intonation so as to speak with a single voice within the choir. Then, and only then, can the chorus effectively woodshed its balance, interpretation, and collective performance.
Which level of deliberate practice matters most? The individual, because it's the foundation upon which the other levels depend and without which the other level's efforts at deliberate practice probably won't amount to much. Ours is a communal art, but one that depends on the deliberate dedication of each of its member.