audibly tone

[ibex]

Hi,

I've just bought a new music book and the cover says, "for audibly tone and unit of rhythm". Could anyone explain that chunk of grammar to me, please? I simply don't understand. According to my knowledge, an adjective should be used here, so that it would read "for audible tone".

Thanks in advance,
Ibex

[tiorthan]

Looks like an automatic translation to me.

[ibex]

Thank you for your answer!
I didn't understand this use of grammar either, but it's on the cover and I would find it very strange if it was a mistake and no lecturer or anybody else had noticed. So it's definitely incorrect?

[tiorthan]

It looks like that to me. It's ungrammatical, however it might still be that this is some kind of terminology I have never heard of. They, sometimes, don't follow all rules.