This is a great improvement for all Boehm clarinets and highly recommended. When moving from F#/C# to E/B you have an impossible challenge. When doing so your F/C key will always be open for a short time, which interrupts the airflow creating a small disturbance and extra key noise.
The Alternated C#/F# Mechanism allows you to play the F#/C# and then to press the E/B key without needing to lift the F#/C# key. A perfect move (and you dont even have to practice it!) This mechanism has been standard on German clarinets for decades.
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