10. A speech producing apparatus as claimed in claim 9, wherein: said control means further includes an unstressed syllable pitch pattern assignment means for assigning to unstressed syllables a pitch pattern slightly falling in frequency except if when the unstressed syllable is immediately following the first secondary accent syllable whereupon a pitch pattern generally stable in frequency at an elevated frequency is assigned to the unstressed syllable.
10. A speech producing apparatus as claimed in claim 9, wherein: said control means further includes an unstressed syllable pitch pattern assignment means for assigning to unstressed syllables a pitch pattern slightly falling in frequency except if when the unstressed syllable is immediately following the first secondary accent syllable whereupon a pitch pattern generally stable in frequency at an elevated frequency is assigned to the unstressed syllable. 11. A speech producing apparatus as claimed in claim 10, wherein: said control means further includes a delta pitch assignment means for assigning an initial delta pitch to each syllable, said delta pitch which is assigned generally falling except for primary accent syllables which have a delta pitch of an increased frequency in falling mode and of a decreased frequency in rising mode, and said delta pitch which is assigned being restricted to differing predetermined limits for (1) any syllables prior to the first secondary accent syllable, (2) any syllables between the first secondary accent syllable and the primary accent syllable and (3) any syllables following said primary accent syllable.