In addition to a rating of the pianist’s performances of the individual works from his or her discography, this guide includes a commentary on five key aspects of the pianist (listed below), each of which is accompanied by a numerical rating. As with essentially all subjective rating scales, it should go without saying that the “grade” assigned does not constitute any sort of mathematically precise value but is simply intended to give the reader a general idea of how I think the particular artist stacks up in the pianistic pantheon, both overall and in specific areas, which I elaborate on in the commentary. It cannot be emphasized enough that the ceiling for the rating scale used in this guide is extremely high since the vast majority of the pianists considered here were deemed world-class in their day and many recorded for major record labels. A mediocre pianist compared with other world-renowned contemporaries would doubtless be an excellent one next to the typical conservatory graduate or garden-variety “professional” who teaches in some obscure state-college music program.

The five categories considered in the overall rating are:

• Solo interpretation (20 points)—The most heavily weighted component in the rating since—at the risk of stating the obvious—solo works typically constitute the largest part of a classical pianist’s discography and solo playing is generally the best indication of the pianist’s musical personality, technique, and wider historical significance. An important factor in this assessment is the pianist’s ability to bring his or her own personal touches to the musical work while simultaneously assimilating a particular period’s and composer’s style effectively. In other words, the pianist ideally should have the capacity to formulate an individual statement or “interpretive argument” regarding the work in question as opposed to subjecting the listener to one more dry recitation of it.
• Collaborations (10-point scale)—An evaluation of how the particular pianist works with other musicians in a group setting. Works in which the piano plays a significant interpretive role will be considered (e.g., concertos, string ensemble, piano four-hands) but not performances with singers, in which, I believe, the pianist generally tends to play the role more of an accompanist than an interpreter. 
• Technique (10-point scale)—An assessment of the pianist’s technical ability as exhibited on recordings. Note that, in this context, “technique” refers not merely to note accuracy or superficial evenness—though important, this is in my opinion a stupid obsession of all too many pianists and critics today—but, in the words of Wanda Landowska, to a complex “strategy of the hands.” On the piano, it specifically involves execution of a wide swath of elements as well as certain general characteristics. These include scales, arpeggios, octaves, double notes, touches (e.g., legato, staccato, portato), tonal balance, clarity, fluidity, control over dynamics and rhythm, seamlessness of velocity, lateral wrist flexibility, pedaling (e.g., una corda and damper usage), posture and deportment, and the list continues. 
• Versatility (5 points)—A judgment related to the pianist’s ability to adapt to various periods and styles of repertoire (e.g., Baroque vs. Romantic, salon music vs. classical sonatas, Scarlatti vs. Prokofiev). While it is much more important to play in one style superlatively rather than 10 styles poorly, a multifaceted pianist should, I believe, receive an additional small plume in his or her hat.
• Legacy (5 points)—A rating of the influence the pianist’s recordings have had on subsequent generations, including the artist’s recognizability and the availability of his or her recordings. Though the opinions expressed in this guide may sometimes fly in the face of modish critical tastes, I believe it is important for objectivity’s sake to reflect the pianist’s likely current reception in the overall assessment, even when I think the actual aesthetic quality doesn’t merit the rep.