Treble clef, sequenced by harmonic series. Choose B♭ or C and the mic listens to the sounding pitch.
note 1 of 4 · written
sounds B♭ on your B♭ horn
open · partial 2
play it on your horn
mic off
Tap start mic and play the note on your trumpet. The needle listens to the sounding pitch (B♭), so it works whether you set the horn to B♭ or C. Center the needle and it locks green.