By starting the major scale pattern on the note F, it is possible to create an F major scale. In this scale, it is necessary to flatten the 4th degree from B to Bb to maintain the correct pattern of tones and semitones.
Here is the F major scale written in standard notation with the scale degrees written under the notes. The B flat note is played by inhaling through the 3rd hole and pressing in the slide.
This melody is derived from the F major scale and is therefore said to be in the key of F major. Play all B notes as Bb as indicated by the key signature.