If you played an E♭ clarinet, you would use the same fingerings you use on your B♭ clarinet. When you play sheet music for a B♭ clarinet, the notes sound a full step lower than the written note. Play the same note on an E♭ clarinet, and it sounds a minor third higher. The arranger handles the key changes when transposing the music, so a clarinetist can use the same fingerings when switching between instruments. Unfortunately, music for trombone is written in concert pitch. So the slide positions for an E♭ alto trombone will be different than the positions on a B♭ tenor trombone.