27.  All  the  melodies  hitherto  considered  have  been  short  and
simple.  But  it  will  be  easily  seen  that  some  additional  rules  are
required  when  longer  and  more  complicated  compositions  have  to  be
analysed  from  a  melodic  point  of  view.  If  period  be  added  to  period,
and  phrase  piled  upon  phrase,  without  any  order  as  to  pitch,  length,
rhythm,  or  modulation,  no  good  result  can  ever  be  obtained.  There
must  be  intelligent  design  in  order  to  secure  the  attention,  interest,
and  comprehension  of  the  listener.  And  the  first  consideration  should
be  symmetry  of  rhythm  between  the  periods.  It  is  a  very  general  rule
that  every  period  should  be  followed  by  a  companion,  or  answermg
period,  with  exactly  the  same  rhythm  as  itself.  The  melodies  hitherto
quoted  have  been  all,  more  or  less,  constructed  on  this  model.  Their
periods  for  the  most  part  run  in  couples.  Each  couple  may  differ  from
other  couples  as  to  rhythm;  though  the  variety  of  good  rhythmical
forms  is  by  no  means  great.  The  most  satisfactory  periods  are  those
which  consist  of  four,  eight,  or  sixteen  bars.  The  next  best  are  those
consisting  of  three,  six,  or  twelve  bars.  Periods  formed  of  other  numbers
of  bars  generally  produce  a  limjaing  or  halting  effect  on  the  mind,  and
should  not  be  taken  as  models.  At  the  same  time  a  few  good  examples
may  be  found  of  melodies  containing  periods  or  phrases  of  five  bars ;  when
such  is  the  case  such  periods  or  phrases  should  always  be  accompanied
by  a  similar  companion.  As  an  instance  of  a  melody  thus  formed,
none  perhaps  can  be  fovmd  more  successful  than  the  old  French  air
"Charmante  Gabrielle,"  which  consists  of  two  periods,  the  former
containing  six  bars,  while  the  latter  is  composed  of  two  companion
phrases  of  five  bars  each.
