manual beaming and variables

[Gianmaria Lari]

Need some help. This works:

\version "2.19.60"

note = {a8}

{

  {\note b b b}

}

but if I explicitly set the beaming like this

\version "2.19.60"

note = {a8}

{

  {\note [b b b]}

}

it doesn't compile. Why and how I can fix it?

Thank you, g.