Junior Euphonium: Audition Solo 1C, Allegretto grazioso
This melody has many dynamic and articulation details. The advantage will go to the players that observe them. If there is a marking on the page and it does not influence the sound then the ink is wasted. Follow the slurs markings carefully. A common error is to not hold the half notes in measures 2 and 4 their full value. Check with a metronome to make sure the first notes of measures 3 and 5 are right on the click. The same comments apply to measures 10 and 12. In measure 21 the D half note (E in treble clef) is a little flat and may sound better in tune if you finger it 1-2. If you are not careful the "a" ending is easy to rush. Hold the half note in measure 38 its full value by releasing it on the downbeat of measure 39. That will help set up the rhythm for the last two bars.
Clinic Euphonium: Audition Solo 2D, Andante cantabile / Poco agitato
This study is challenging for its long, slurred phrasing. Make sure you play them with a steady airflow. Huffing the wind to assist with the pitch changes is a common error that detracts from the smoothness. There are quite a few articulation details in the third and fourth lines. The advantage goes to the players that observe them all. In measure 11 the downbeat D (E in treble clef) can sound a little flat when played open. Playing the D and the G (treble E and A) with 1-2 usually makes for a better in-tune interval. Another common error is to play the fermata in measure 16 too short, especially coming off the ritardando. A good rule with fermatas is to count the rhythm of the note first, then hold it.
Senior Euphonium: Audition Solo 3F, Allegro
The first measure is marked scherzando, in a light, playful style. That is easy enough for the first four measures, but after that it jumps to the forte/fortissimo dynamic range. The style will change, but be absolutely careful to keep the tempo steady. The tempo marking says quarter at 112, and that can be a challenge. If that speed feels a bit frantic then adjust the tempo down slightly, (NOTE: the recording is purposely under the marked tempo). A confident performance at a slower tempo is better than a ragged performance at the marked tempo. The composer is very detailed with the articulation markings, so pay attention. Measure 24 with the accent and two slurred groups is a good example.
Download these performance notes [pdf].