Sounding out a double-stop over the change of string is a way to practise a round bow in string crossing.
In performance, make the crossing between strings slightly faster, to avoid sounding the double-stop.
Experiment with how slow and steady you can make the string cross while maintaining clear articulation.
This excerpt is Bar 18 from "Sicilienne and Rigaudon" by Kreisler.
SEE
Scores - String Crossing in Rigaudon - violin & viola
Resources - Repertoire
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