C preprocessor tokenization does not expand macro?

Question

1) Why is the macro MSG not expanded in the following expression?

#define MSG Hello
#define HELLO(name)  MSG ## name

void HELLO(Dave) () {}

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Answer 1

#define MSG Hello
#define cat(x, y) x ## y
#define cat2(x, y) cat(x, y)
#define HELLO(name) cat2(MSG,name)

Live demo @ ideone.