I use it all the time exactly for expression when I think it is required. accordion is one good example. Also, sometimes the volume I have set may not be appropriate for the situation and it needs to be adjusted up or down on the fly !!
Ray
Are you saying that you are controlling your arranger from a MIDI/digital accordion, or playing the accordion patch in the arranger with an expression pedal?
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"You Shall Know the Truth, and the Truth will set you free." John 8:32