These type of horns can be thirds, fifths or fourths .. sometimes intentionally only a step apart even. It usually doesn't take long to figure them out as they are often only a couple different notes being played by multiple different instruments.

Example:
Trumpet playing C-Bb-C
Sax playing G-F-G
Bari Sax playing C-Bb-C (octaves below trumpet)

Often the Bari sax will lead in on a note or two and then other horns join in as above. In example above the Bari may play Bb-C with the C landing a beat before the other horns join in.

More difficult is a mix of horns playing a 'splat' chord .. these are often a little harder to voice correctly and use more complex chords.

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