How to recognize modulations by ear?

1. How to identify modulations?
2. How do you modulate to the subdominant?

How to identify modulations?

Look for the following cues when examining music containing modulations:

1. Look for recurring accidentals, then add them to the key signature to determine the new key. ...
2. If accidentals are canceled out, they indicate tonicizations or chromatic non-chord tones.

How do you modulate to the subdominant?

For example, relative to the key of C major, the key of F major is the subdominant. Music which modulates (changes key) often modulates to the subdominant when the leading tone is lowered by half step to the subtonic (B to B♭ in the key of C).