Play (sing) as if you could not speak.
Music which assaults the mind and restricts it with a numbing drone, commands the brain not to think and holds thought hostage while it rapes the ear. (This includes all music in which there is insufficient change of activity in one or another element of the musical texture. Much jazz radio programming falls into this category.)
Become conversant with harmony by employing the conceit that it doesn't exist. Discover the appropriate chords by looking at everything as if it were counterpoint. This works as a general principle from the simplest textures to the most complex. In order to achieve comfortable familiarity with this idea, make it concrete by learning the basic rules of seventh chord voice leading so well that they become as instinctively subconscious as the rules of English grammar. When the roots move by 4th or 5th; the 3rds lead to the 7ths, and the 7ths lead to the 3rds. When the roots move by step; 3rds lead to 3rds, and 7ths to 7ths.
Any note longer than a quarter needs shading. Dynamics need to be changing almost constantly and on several scales. One must take for granted the need for emphasis, de-emphasis, variety of articulation and nuance. The interpretation of music is a constant search for understandable change (no less in improvised passages than in written out ones). Shade pitch, vibrato and dynamics on every long note. Take every opportunity to express nuances.
A written out background, unless it is rhythmically neutral (chorale - like), quickly becomes a dominant force in the music. A soloist ignores the presence of such a background at the music's peril. The entrance of the background changes the soloist's role from that of primary focus to one of necessary, but secondary embellishment. When this occurs, choices of gesture, range, texture and especially phrase length and spacing must be made in intimate and optimal relation to the written ensemble passages.
Practice accuracy of timing as if your life depended on it. A trapeze act provides a good model.
Fast notes are perceived as louder than slow notes. Performers must work opposite to this tendency.
As voicings spread, individual parts must be played more firmly; less so as voicings converge.
Crescendos must be extreme at the end; decrescendos extreme at the beginning.
It's as silly to claim that one is prepared to perform a piece of music when one knows only one's own part as it would be to claim to be prepared to perform in a play knowing only one's own lines.
Bands are generally much too loud most of the time and often not full enough sounding in loud passages. In terms of dynamics (and incidently, pitch) the bands of Count Basie and Gerry Mulligan offered consistently good examples.
One of the drummer's main (and too often ignored) responsibilities is to lay out the form of the composition with changes of pattern and fills.
Drummers should play immediately much more softly after a break or fill.
The rhythm section must be constantly shading, no less than any other element in the ensemble. Amplification for the piano should not be necessary and always bloats the sound, destroying balances in the rest of the band.
Making music on wind instruments is not just blowing and fingering. Each note must be individually set and tuned.
Standardization can be a boon to industry but is not pertinent to art.
Great music happens most often when the eyes are closed.
It is essential to recognize the differences between music which is strong and music which is forced; music which is relaxed and music which is weak; music with energy and music which is frenzied.
Few notes on the page do not mean "nothing to express or project." Conversely, many notes do not mean all meaning is explicit and no further thought and interpretation is necessary. In both cases, the implicit meaning must always be inferred and expressed by the players. The idea that a page full of notes and busy rhythms has enough music to preclude the necessity for interpretation is an illusion to be unlearned over and over.
Most interesting music has a preponderance of "negative" accents. Accents and "ghost" notes enliven all lines.
A fortissimo doesn't mean to play every note as loud as possible from the beginning of the phrase to the end. It means that the predominant dynamic is fortissimo.
The fun doesn't half begin until the details are developed.
"Swinging" requires the playing of each rhythmic figure with total accuracy and abandon while maintaining the ability to shift to a new rhythm instantaneously with equal commitment.
While it is essential to create the image of an ideal performance in the mind in order to maintain a standard of comparison, it is dangerous to remember the ideal too well during a performance. It is all too easy to "play back" the idealized version, allowing memory to obliterate consciousness of what is actually being achieved by the performers. Mistakes in balance are most susceptible to this phenomenon. If one doesn't listen carefully to what is really happening in the room, compensation for gross imbalances may be applied to the "inner ear" rather than actually adjusting balances at the source so that they arrive at the ear correctly.
Bass lines generally need even rhythm with dynamic accents and breathing, swells and releases. It is often a good idea to make a crescendo through the final dominant chord of a phrase and to get suddenly softer on the resolution. Bass amplification level must be kept low enough so that the bass is not heard in full ensemble passages above mezzo-forte or the sound will dominate all activity and level everything. When it is necessary to hear bass notes in loud passages, they must be supported in other instruments (guitar, piano, baritone sax, bass trombone, tuba).
It is impossible for an educated listener to take seriously any music with a sound quality that is the musical equivalent of a painting done exclusively in Day-Glo colors. This includes the work of several commercialy successful "jazz" guitarists whose constanly applied electronic effects create just such a result; “Franchise Jazz”.