Being able to play across the harmonics without tonguing is such an advantage as a trombone player, and I find that many trombone players do not utilise this technique. For instance, the F on the line in the staff and the G above it, on the space in the staff, are on separate harmonics. Moving from 1st to 4th position, you are breaking across this harmonic or playing "against the grain." This makes a natural break in the sound and therefore, you do not need to tongue the note. As a trombone player, trying to keep up with the more fleet instruments like the trumpet and saxophone, you need all the tricks you can get, and a few intervals where you do not need to tongue help tremendously. Not only that, but the natural "tongue" or break is clear and matches a "ta" or "da" tongue quite well. If you get in the habit of playing through the lines, without tonguing, this will also help as you play in the upper register where the harmonics are so close together that tonguing is optional at times.
Dr. Michael Kearns
Musician, educator, husband, father, web designer ... my life is like a mosaic with each piece vying for my attention.