MODULATION  

1. DEFINITION OF MODULATION: Modulation is the process of changing from musical key to another key in a musical piece.
2. TRANSPOSITION: Transposition is the process of changing the pitch of a composition without other changes .Transposition occurs by raising the pitch of the music piece in the key to D major

Transposing instruments include clarinet, saxophone and trumpet, characterized with B flat transposing a tone written above.

Saxophone Alto E flat transposes a minor 3rd.Trumpet transposes in A, horn transposes in F.