As a result of lessons learned in the Alessi Seminar in 2007, I have revised my thinking on this subject.
HOW FLOPPY THE WRIST?
It is not a good idea to allow the wrist to flop around loosely during slide manipulation. This leads to an uncoordinated slide.
HOW TO HOLD THE SLIDE
It is best to hold the slide with the thumb and two fingers. Keep the thumb straight. Mr. Alessi has compared this to holding your car keys. The fingers should be slightly curved. You slide grip should be firm but comfortable. Mr. Alessi has pointed out that a relatively firm slide grip improves the connection between the slide and the brain.
A GAME OF OPPOSITES
Pretend to conduct legato music. You will probably attempt to convey smoothness through smooth, flowing gestures of your arm. Conversely, staccato music might be conducted with sharp, quick arm gestures.
While playing legato, however, it is necessary to snap the slide quickly and lightly from one position to the next. Slow slide movement will result in sloppy glissandi between notes. In other words, to play legato, you must move your slide arm in a manner opposite that which might be used to conduct legato. Students playing legato music often allow their slide arms to move in a legato manner, creating undesirable smears between notes.
LEGATO MUSIC REQUIRES A 'STACCATO' SLIDEConversely, if you are playing short notes, you have more time in between notes to get your slide from one place to the next. Thus it might be said that staccato music allows for a more "legato" slide as well.
ONE THING AT A TIME
I believe that one of the secrets of a good sound is the perfect coordination of slide movement and tone production. Often I hear a student whose potentially wonderful sound is marred by sloppy slide work. For example, in a passage of legato eighth notes students often begin to move their slide away from a note before they have actually finished playing it. The end result is a mini-glissando between their notes which creates an overall impression of sloppiness and uncentered playing.
This type of error always reminds me of a football receiver who takes his eyes of the ball just before it arrives. The receiver may be already planning his run but often ends up dropping the ball instead.
GLISS PRACTICE
Try playing a legato passage without using the tongue. Where natural slurs
do not occur, you will get glissandi between notes. As you play, make these
glissandi as brief as possible through quick slide movement and steady flow
of air (see also: silent blowing).
This practice technique is excellent for: (1) improving slide speed, (2) encouraging
steady flow of air and (3) improving embouchure accuracy (especially in passages
with wide intervals).
APPROXIMATE VS. ACCURATE
Students often approximate slide positions during rapid passages. This is particularly noticeable with young students attempting to play a chromatic scale containing low B in 7th position. Since they can't reach it, they move in the direction of the note and then turn around. I believe this then becomes a habit with older players. Even with notes in 6th and 5th position, they reach out and turn around to come back without ever having reached the note!
Another common mistake occurs when a student plays rapid notes successively (for example, in 1st, 2nd then 4th position). The middle note often ends up being halfway in between 1st and 4th rather than falling in a true 2nd position. Most students miss slide positions on the flat side as they extend their slides and on the sharp side as they bring their slides in.