2 [Edit removed during grace period]
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PHP, 171 bytes

preg_match_all('#[A-G\.]|\([A-G]+\)#',$argv[1],$m);foreach($m[0]as$l){if($l=='.')echo".......";else foreach([A,B,C,D,E,F,G]as$a)echo strpos($l,$a)!==false?O:'.';echo"\n";}

Breakdown :

preg_match_all('#[A-G\.]|\([A-G]+\)#',$argv[1],$m); // Matches either one character in the range [A-G.] OR multiple [A-G] characters between parentheses
foreach($m[0]as$l)                                  // For each match :
    if($l=='.')                                     //   If no note is played
        echo".......";                              //     Echo empty music line
    else                                            //   Else
        foreach([A,B,C,D,E,F,G]as$a)                //     For each note in the [A-G] range
            echo strpos($l,$a)!==false?O:'.';       //       Echo O i the note is played, . if not
    echo"\n";                                       //  Echo new line
}

Try it here!