My good friend James Forney, over at Horns2U, has let me share the following article on How to Test a Trombone. Good information if you have a new trombone player in the family.
It can be very difficult to choose a new (or "New to You") trombone.
When comparing several samples, try to play on each of them for a while before you begin more serious testing and comparing. This will give you a feel for the horns and get them working acceptably. Then do the serious comparisons in pairs only. Try two horns thoroughly and choose the best one. Set aside the one you don't like and start on another pair. As you begin to try each pair, start by playing the "new" one and warm it up a little before you resume comparing. Continue this process of elimination until you have gone through all the choices. When you have selected the best of the lot, be sure to try your old horn on the same tests to make sure you are really getting something better.
Pay some attention to the way a horn works mechanically, but don't get too distracted by it during your initial selection process. First narrow the field down to a couple winners. If one of them has some mechanical trouble, attend to it and see if it can be remedied. A horn that has otherwise good playing characteristics is worth exploring a little further. when the valves move and may cause a "buzzing" sound on certain notes.
If the trombone has a trigger, check its operation as well. Do not be too concerned if the action seems sluggish. Many triggers need to be broken in a bit before they will operate smoothly and quickly. And it may take some experimentation to get the right combination of type and amount of lubricant for the slide action. If you are not used to a trigger, it probably won't feel comfortable at first. You need to get used to holding most of the horn's weight with your left hand and still keep your hand free enough to operate the trigger's paddle.
With or without a trigger, make sure your left hand can hold the horn comfortably. There can be considerable difference in the distance from the 3rd valve tube to the other side of the large branch -- your "grip" reach. If you have large hands this may not be an issue, but if you have smaller hands this can be an important factor in avoiding muscle/tendon strain..
As mentioned before, the attack is a very important criterion to test. Much research has been done on the acoustic properties of instruments. In one test from decades ago, instrumentalists played long tones, which were recorded on audio tape. The tape was later played back for musicians to identify. The panelists were able to identify each instrument with little trouble. Then the technicians used a razor blade to cut off the attack of each note (this was obviously before digital recording technology). When this cut version was played, the panel had great difficulty differentiating between any two instruments playing the same exact pitch. A trumpet could not be distinguished easily from a clarinet without being able to hear the attack.
This is a difficult area to assess in any reasonable amount of time. No horn has perfect intonation. You have to find one that has made acceptable design compromises for your needs and playing abilities. However, your impression of the new horn's intonation will be dramatically affected by the intonation of the horn you are used to playing.
USE A TUNER. This is your only hope of judging a new instrument accurately. Be very sure you get each horn warmed up thoroughly before judging the intonation (five minutes will not do it). Then tune it carefully to a concert Bb in the middle register.
Notice three things with any pitch discrepancy:
1. Is it in a range that will be noticeable or problematic?
2. How far is it from true pitch?
3. How easy is it to adjust?
Work with intonation long enough that you begin to feel familiar with each horn. If you are judging a particular note, approach it from above and below melodically to see how that affects it. Remember, you may be used to lipping a certain note up or down because of the horn you have been playing (when you are really used to one instrument, you may not even be aware you are doing it). You may perceive problems in the new horn that aren't there. In order to work around this, you need to find out where the horn wants to play the note. Stay on the note in question; play it loud and soft to get a feel for it. Bend the pitch grossly up and down. This will help you disassociate your previous notion of where to put the pitch. As you bend the note, listen to where it is most resonant -- this is where the horn wants to place it. As you are doing all this in front of your tuner, start with your eyes closed. When you feel like you have found the horn's true pitch on a given note, open your eyes and see what the tuner reports.
There is one more characteristic to observe. Some horns make is easy to adjust pitch by lipping; others make it quite difficult. If the horn is too easy to "bend" on pitches, that may be because it doesn't have a good, solid center. You want a horn that has well-centered notes. However, some horns are so well centered that it can be very difficult to bend a note up or down. That is the point of #3 above -- you have to be able to adjust the pitch as much as necessary to play in tune with a section.
An instrument with superior response can make all slurs easier and cleaner (slurs can be one way to judge response). You will be able to play slurred arpeggios with more facility. For this area of testing, you will probably judge as much by feel as by sound. As with many of these factors, test slurs in various ranges. I suggest testing with melodic slurs, slurs over small intervals (such as arpeggios), and slurs over wide intervals. Be sure to test glissandos with trombones over similar ranges.
Notice if the horn is comfortable to hold. Try it while sitting and while standing. Notice the reach from the right hand-brace (behind the valves) to the valve tops, and notice the reach for your left hand to wrap around the slides as you play. Also, make sure the angle of the mouthpipe is comfortable. Any of these factors can vary between samples within the same brand; try several if necessary. If you have small hands or strength issues, the weight can be an important factor, and it can vary a great deal from brand to brand and even model to model. Some brands have different metal thickness; thicker metal may give you a more substantial sound, but will also be harder to hold in playing position, especially while standing.
Finish: Three Common Choices
Brass instruments are commonly offered in two finishes - gold color and silver color. With modern materials and construction techniques, either color finish can hold up very well for years. Gold finish is almost always due to highly-polished brass coated with a clear (or lightly tinted) lacquer. If it were not coated, brass would begin to tarnish immediately and would soon look uneven and dull. Silver finishes are usually a plated coating on top of brass. Inexpensive horns may use a nickel plating. This is durable, but does not have the clarity of shine that silver offers. More expensive models use silver plating, usually with a bright, shiny finish. They are the most durable for typical players. Some models may use a "satin" or "scratch" effect on the silver finish. This has a duller finish (similar to a shiny silver object that has "fogged" up from humidity). Either type will require some effort to polish them periodically.
Some instruments offer options of two or three of the finishes mentioned above. Lacquered brass is usually the standard choice. Nickel may cost slightly more. And silver usually has the highest cost premium, often $100 or more.
Of course it is best to use a mouthpiece you have been playing on for some time and are used to. If you are going to use the seller's mouthpiece for any of the horns, use his for all of them -- your comparisons will probably be more valid.