Can't get \arpeggio to work

[Bill Mooney]

Greetings,
...from the Notation Manual
"An arpeggio on a chord (also known as a broken chord) is denoted by 
appending \arpeggio to the chord construct:
    <c e g c>1\arpeggio "

I guess you 'do' need to define a chord for it to work - which you don't 
seem to have done in your example
{  \clef "treble_8"
     \time 2/4

     << bf,4 gs4 b4 >>  << a,4 bf4 d'4 >>\arpeggio
}

perhaps this is what is meant??

{
     \clef "treble_8"
     \time 2/4

     < bf,4 gs4 b4 >  < a,4 bf4 d'4 >\arpeggio
   }

Hope this helps
Regards
Bill