Like the saxophone section, the trombone section sounds equally well in close or open position voicings. The trombone voicing is the harmonic foundation for the brass section and will almost always contain the third and seventh of the chord.
Trombones are often used in a rhythm section role, such as the "punches" illustrated below. These simulate the left hand comping of a jazz piano player. Notice that most of the harmonizations are rootless and that the third and seventh are present in each chord. Also, take into consideration the placement of extended harmonies within each voicing. They are all located above the bass clef staff.
Below is an example of root position voicings using five trombone parts. Notice that the third and seventh of each chord is present and that chord extensions are written above the bass clef staff. Quartal harmony is used on beat four of the second measure.
The only harmonized trombone soli found on the CD is from Yes I Do. There are five trombone parts in this example. The top four parts play primarily rootless voicings and the bass trombone plays chord roots.