Alois Hába, Suite für vier Posaunen, Mvt. II, Andante cantabile, mm. 17-20
In this short excerpt, we see the interval of 2.5 semitones expressed harmonically. I find this interval ambiguous: sometimes it sounds like a wide second, and sometimes it sounds like a narrow third. Hába is not terribly consistent with his enharmonic spelling, so sometimes this interval looks like a second and sometimes, a third.