In Italy, a single B♭ clarinet
Earlier it was described how clarinetists play both an A clarinet and a B♭ clarinet. In fact, however, there is an exception to this rule-Italy, the nation of opera. In opera, the key of the music is constantly changing and there is no time to switch instruments. Accordingly, Italian clarinetists have gamely opted to play the B♭ clarinet alone. When they play, they must transpose the score-that is, change several of the notes by adding and taking out sharp (♯) and flat (b) notes as required. This represents a feat of considerable skill. However, it also means that there are occasionally places where they cannot play, due to fingering discrepancies for example, and that manufacturers receive orders such as "Please make a lever for trilling" or "Please make extra keys."