A concert is a unique moment, in which artists have the opportunity to transmit their ideas and emotions directly and intuitively to the audience. However, there are many elements that influence the acoustic and emotional communication of the music: this doesn't just depend on the expressive intentions of the performer, but is partly determined by the musician's physical and psychological conditions, as well as by a number of external parameters, which can vary from one day to another, and even during the same evening.
Of course, the instrument has a fundamental influence: it can undergo notable changes due to the oscillations in temperature or humidity, and can take on a completely different sonority resulting from the acoustics of the hall. For pianists and organists the problem is more complex, as they have to obtain the maximum from an instrument they don't know, and which may be very different from their own. In the piano, for instance, the variables are numerous: the timbre, the dynamic response, the duration of the sound, the weight and action of the keyboard, and even the size of the black keys, which can vary in length or in their tapering. The technical preparation of the piano, which includes the tuning, the intonation and mechanical management, is another particularly important element: many pianists are well aware of how the same instrument can improve immensely if it is looked after by a first class technician. Also the stool can create no few problems: it can be noisy, unstable, inclined or not perfectly adjustable, and it no surprise that many prefer to bring their own stool with them.
The stage is a determinant element for the success of a concert. In many older theaters it is not flat, but slopes down towards the stalls, forcing the players (especially pianists) to play with a shift in the center of gravity. In the most “serious” cases, wedges are placed under the right-hand wheel of the piano; logically speaking, these should also be put under the stool, to keep it at the same level. These points may seem trivial, but taken together they require a particular adjustment to be made in calculating the distances and the strength to exert on the fingers, which often also affects the artistic outcome of the performance. It comes as no surprise, then, that the most meticulous pianists go round with a spirit level to check the inclination of the keyboard!
The acoustics of the auditorium can significantly enhance (but also ruin!) a concert performance. A good hall should in fact offer performers a reliable audio feedback on the stage, allowing them to constantly check their work and stimulate them to strive for further expressive details. On the contrary, poorly functional acoustics, whether too dead or too resonant, could force the artist to radically modify certain performing parameters (speed, dynamics, articulation), notably placing at risk the efficacy of the communication.
The performer's concentration is subject to a wide range of sonic or visual disturbances present in the hall: these often have a determinant affect on the performance. Regular noises, like the ticking of clocks or the dripping of water, can have a "metronome effect" that creates an interesting play of polyrhythms... Also the lights and colors that surround the performer influence the rendering, at times altering the acoustic perception of the sounds. The relations between vision, hearing and smell have been the object of numerous scientific studies, which revealed highly interesting consequences on the sensory capacities. This is also true, of course, for the listeners.
The sounds coming from the audience constitute a more complex problem, as the artist perceives them for the most part as a reaction to his performance. Even an innocent cough may therefore be interpreted as a symptom of insuccess, or at least of insufficient expressive tension. The relation with the public differs at each concert. The artist always tries to get a precise idea of those he is addressing, sometimes picking out one or two faces that inadvertently become his interlocutors, and perhaps trying to understand their reactions during the applause. Hardly anyone believes it necessary to change their interpretation on the basis of the type of audience being faced, and yet this happens very frequently, almost always unconsciously. It is only natural that, if a certain complicity is created between the listeners and the artist, he will be more at ease, will sense their trust and will know how to give the utmost to satisfy their expectations. On the contrary, if he feels a diffidence depending on the type applause, the noises from the hall, or simply through his own instinct, then the concert will be all uphill. So it is best to get to know the habits of the different kinds of audience, and thus avoid misinterpreting their reactions: it is useful to know, for example, that in Tokyo there is less applause than in Mexico City, or that the whistles in New York have the opposite meaning to those in Milan.
There are, moreover, some elements that are easily overlooked, which influence the rendition of the concert artist: the atmospheric pressure, the temperature, the hours of sleep, the alimentation, family worries, the success of a soccer team he supports, and many other aspects of everyday life. Each artist tackles these problems in a different way: some shut themselves away for several days before the concert, or listen to a soccer match until it's time to go on stage!
The aspect that musicians place the greatest importance on when preparing for a concert is studying the items on the program. They try to limit the margins of error to a minimum, so as to be able to face and resolve at best all the unforeseen circumstances mentioned above. In my opinion, though, there is no perfect cause/effect ratio between the quality of technical preparation and the outcome of a concert. Often a hyper-rehearsed program, polished down to the finest detail, is less successful than another more difficult one, prepared in less time. This doesn't depend only on external factors, but also on the greater amount of attention and effort put into concerts that are most "at risk". And the awareness of not having adequately perfected all the details may also have a positive effect, inspiring the search for the extemporary magic that will make the concert a unique and meaningful experience for the audience. The meticulous preparation of a program serves mainly to help the perform feel psychologically confident, but may sometimes turn into a disadvantage if it ends by limiting the creativity of the concert performance.
In conclusion, the major part of what influences the outcome of a concert is independent of the good will of the artist. However, the performer can make his life easier by managing to achieve a level of concentration sufficient to forget what might disturb his rendering. Concentration does not mean, though, shutting oneself off totally from the outside world. On the contrary, musical creativity is fed precisely by extra musical stimuli, and, as is obvious, the more the artist has deep and varied experiences of life, the more his music will be equally rich and interesting.
Performance, moreover, cannot be hermetically conserved the same for ever, but naturally adapts to the human contingencies of the individual and of the culture that surrounds him. This is why it is basically useless to try to copy from other artists, or pursue a perfect idea of performance based on the memory of a particularly successful evening: the same identical interpretation might not be suitable for a different context, and would prove scarcely effective in terms of emotional expression. All things considered, music exists only on the basis of how it is perceived by each one of us. The greatest concern of a concert artist should therefore be to communicate in the best possible way his own ideas and inner feelings, through the musical message left to us by the great composers of the past (or, why not, of the present).
We are moving towards a world in which technical perfection and objectivity risk becoming an obsession. Maybe it is the task of music, of those who produce it and those who enjoy it, to ensure that the poetry and unpredictiveness of art continues to enrich and enhance our lives.