Does 'alla breve' mean, you play double as fast?

[counterpoint]

I hear this so often. But personally I don't think so.

alla breve for me just means, you count slower.

[zezhyrule]

It means cut time. Time sig of 2/2. Irrelevant to the tempo, just affects the pulse.

At least that's what I know it to mean.

[mike_lang]

I hear this so often. But personally I don't think so.

alla breve for me just means, you count slower.

It doesn't mean that at all; just that the music in "in 2."

[counterpoint]

It doesn't mean that at all; just that the music in "in 2."

Counting half notes - yes, that's what I meant with "counting slower" 

[mike_lang]

Counting half notes - yes, that's what I meant with "counting slower" 

If you mean that you count beats half as frequently as in 4/4, I'll buy that.

[counterpoint]

If you mean that you count beats half as frequently as in 4/4,

Yes. But I do not sell anything 

[iansinclair]

It means cut time. Time sig of 2/2. Irrelevant to the tempo, just affects the pulse.

At least that's what I know it to mean.

Quite so.  In 4/4, the "normal" accent pattern is (relatively speaking now!!!) Loud soft medium soft | loud soft medium soft etc.; in "cut time" -- 2/2 -- the "normal" accent pattern is Loud soft | Loud soft etc.