As the bell is smaller than a modern trombone, the harmonic series is closer to a perfect harmonic series, which is the basis for just tuning. Without adjusting the slide, the first to second harmonic is a perfect octave, second to third harmonic is a fifth slightly wider than equal temperament and fourth to fifth harmonic is a major third slightly narrower than in equal temperament. These adjusted intervals make chords ring and are the basis of meantone. In fact, Daniel Speer says “Once you have found a good C (third position), this is also the place you will find your F.” Playing a sounding C and F in exactly the same position on a modern orchestra sounds out of tune, but it tunes perfectly well on in a sackbut choir if everyone plays natural harmonics.