Write music for the trombone in the bass clef.
Choose a key signature for your music. Trombone players prefer music written with flats. You can write music with sharps, but flats are better suited to the instrument. The best keys for trombones have one to three flats in the key signature. The more flats you add, the more awkward the music becomes.
Begin writing your melody. Remember the trombone range is only E2 to C5. Aim for a range in the middle of this register. The best range for a trombone is F3 to G4.
Include glissandos if appropriate to the music. Glissandos are indicated by a wavy line that stretches between two pitches. The trombonist will smear the notes in between the two notes to create an impression of a blurred scale.
Add articulations and dynamics to indicate how each note should be played. The most common articulations are accents that create a sharp emphasis on a note, legato that connects notes together with a slur and tenuto lines above the notes that indicate to play each note the full value.