Background
Writing in the early part of the 20th Century, Matthay sets out his theory of 'Musicianship' and 'Executantship' in Part 1 of his encyclopaedic text on pianoforte playing, "The Act of Touch". Matthay's basic premise is this: Musicianship consists of our power of understanding music; it is the combination of our musical-emotional and musical-intellectual abilities, which form our conception of the music as a result of sense perception. But, Matthay goes on to say, without the technical means to act upon this, we are lacking the power of musical communication; that is, we are lacking the physical and muscular capacity to act upon our musical intentions in the act of playing. Therefore, in addition to developing our Musicianship, we must equally seek to culture our Executantship–the power of expressing and acting upon such objects of musical perception as occupy our musical imagination.
Application
On this basis, with my pupils (and in my own study) I like to consider Interpretation as a two-step process in which these musical and executive faculties are separated into two stages, the end-goal being the synergy of these two faculties into the singular act of playing.
Taking a short passage or phrase of music which presents a suitable range of detail–such as the one which follows–I first explore the music conceptually with the pupil, and secondly guide them in linking this with muscular sensations, which allow them to realise the music through the medium of the instrument.
Step 1
Looking at the above example, and using their imagination, I ask the pupil to mentally explore the music. In this stage, we are culturing the eye-ear-mind (visual-aural-mental) relationship that stimulates and drives musical perception. In the short passage given above, I'd encourage and explore the composite elements, which–for the sake of discussion–might include the following:
The notes form a five note pattern, lying under the average hand, ascending by step, and returning by descent to the same note which began the pattern. I invite the pupil to hear this in their mind, even if only relatively (according to the level of development of their musical imagination);
There is a slur over the music, which is a depiction of the musical journey. The pupil should experience this intellectually as: 'from–to'. The art of phrasing lies partly in sustaining a dual attention upon both the musical activity of the moment and the point of destination, and experiencing this point of arrival emotionally and intellectually. I often like to place arrows at the end of slurs to highlight this sense of journey. The five notes are given a structure and a destination. A useful exercise is to ask the pupil to sing these notes mentally whilst drawing a curve in the air to show the shape of the phrase;
There are staccato marks on each of the notes, which tell us something about both the duration of the notes and, potentially, their tonal quality. Again, I would ask the pupil to explore how these manifest in their imagination. I often like to introduce analogous movements or sensations which may provoke a useful and suitable experience in the mind of the pupil;
Finally, there are hairpin dynamics, which point towards the climax of the phrase or passage through the use of dynamic (i.e. tonal quantity). The pupil should, again, seek to hear this in their imagination, as the tonal gradations are layered onto the pattern of notes.
This process may only take several minutes in total, but it is the groundwork by which the pupil assimilates all of the necessary information that will determine the corresponding and complimentary physical and muscular gestures, which in turn lead to the realisation of the correct sounds through the instrument. Using a cumulative process, by the end of stage 1 the pupil has developed an increasingly complex conception of the music from the notation. Having achieved this, to some degree or other, the pupil moves to Step 2...
Step 2
Now comes the moment to teach the correct muscular conditions which will help the pupil to realise their conception of the music with increasing precision. Each element is a separate challenge, but eventually the elements coalesce into a singular and unique musical-muscular gesture:
The notes form a five note pattern: By and large, the pattern can be played by a movement of the finger (perhaps with sympathetic movements of arm and hand), with co-operative condition and position from the other components of the playing mechanism. Challenges might include: position of the hand; correct finger technique, and; barely perceptible lateral movements which support the correct action of individual fingers;
There is a slur over the music: In order to realise this as the manifestation of the phrasing, an underlying consistency of exertion in muscular engagement (to some predetermined degree) will be necessary for the duration of the phrase in toto. The process of demarcation should also include correct timing of: a) the beginning of exertion, and; b) the muscular relaxation which follows the conclusion of the phrase. Thus phrasing becomes both a mental and a muscular experience;
There are staccato marks on each of the notes: In simplest terms, these marks are a matter of duration of tone (admittedly, this must, under most circumstances, be coupled with consideration of other contextual musical factors, but I'm being simplistic here in order to focus on the methodology, which aims to be cumulative). This question of duration manifests itself as the relationship between: a) attention, through aural perception, to the commencement and cessation of sound, and; b) timed muscular exertions made in response to judgements made using the aforementioned attention through aural perception;
Finally, there are hairpin dynamics: These are indicative of some degree of increase and decrease in exertion, proportionately distributed across the given notes, in order to bring about the effect of climax at a particular moment.
Conclusion
This could form a much longer and in-depth discussion, and I would like to explore in greater detail some of the things I've touched on above. But in the interests of simplicity, what I have broadly laid out is the two-step process which I use to guide my own Interpretation and which I try to encourage in my students, tased on Matthay's theory of pianoforte playing. It comes down to: concomitant development of the Musical and Executive faculties, and the rendering of the music through an understanding of how the technical facility of a player allows (or limits, as the case may be) their ability to act upon and communicate their musical imagination. The intended result is a homogeneous musical-muscular gesture, which brings together multiple layers of both intellectual and physical development, manifesting outwardly as a singular act in the realisation of the music through the instrument.