Topmusicanswers
The problem is that both double stops use the same fingers, but on opposite strings. Assuming first position, the first double stop uses second finger on D string and first on A string, and the next note uses first finger on D string and second on A string.
When should a violinist learn double stops?
By the time a child or an adult can play simple tunes, they are already ready to start playing two notes at the same time - I mean easy double stops, not fingered octaves! Once they are able to play single-note scales with shifts, by definition they are ready to start on double-stop scales.
Why is a double stop called a double stop?
This is actually a violin related thing. In violin, when you finger a note it is called a stop, so when you finger two notes, it's a double stop. It's just been carried over to guitar.
