I am trying to understand the working of an old computer speech synthesizer (SAM for the commodore64) which uses a series of rules to break English text into a string of phonemes. The rules make some frequent tests for membership of the following letter sets:

//  0x04        [ D J L N ]
//  0x08        [ B D G J L M N R V W Z ]
//  0x10        [ C G J S X Z R S T Z ]

Is anyone able to spot what traits the following sets may have and why they are significant?

Would I be correct in thinking the 0x10 set are fricatives?

Thanks in advance for any insight you can provide.

  • 2
    What are these? Letters typed in English? Codes for individual phonemes? How does the synthesizer work? What's the input like?
    – jlawler
    Feb 7, 2017 at 16:42
  • Since it was said that the code is there breaks English text into phonemes and to sort letters into groups, I suppose these are actual letters rather than symbols encoding phonemes.
    – lemontree
    Feb 7, 2017 at 17:25
  • For all letters, there are associated 'flags' which denote that the letter belongs to a specific set (the meaning of each set is what I aim to deduce.) One letter can belong to multiple sets. So above, the letters D,J,L and N all belong to one set, which the computer marks with the number 0x04. As an example, here is a rule defined by the system: ``` '.(S) =Z' ``` Feb 7, 2017 at 18:01
  • If the rule on the left hand side of the = is matched then the Phoneme encoded in text on the right hand will be output. As best I can see, the '.' here will match any of the characters in set 0x08. The ' ' character on the right hand side of the parenthesis will match against any letter at all. The rule as a whole will match any letters in set 0x08 if they are followed by a 'S' character and any other alpha character. I'm not sure if that will clear anything up, but hopefully is shows a little more of the context for this question. Feb 7, 2017 at 18:06
  • 2
    This resembles regexp methods of decomposing segments into features, without particular concern for phonetics. There must be more that just 3 such sets: the "meaning" of the sets would emerge from looking at what all of the sets are, e.g. what other sets is "D" a member of? "R" is in x'08, x'10, "L" is in x'04, x'08, so inferring the "meaning" would require having the total list.
    – user6726
    Feb 7, 2017 at 18:41

1 Answer 1


I don't get the full pattern, but there are some common properties:

  • D [d], L [l], N [n] are all voiced alveolar consonants; J (usually pronounced [dʒ]) is postalveolar
  • [ B D G J L M N R V W Z ] are all voiced; [ J L M N R V W Z ] are also sonorants, but [ B D G ] are not
  • C(when pronounced [s]), G (when pronounced [dʒ]), J ([dʒ]) S ([s] or [ʃ] in "sh"), X ([ks]) Z ([z]) are sibilants; however G when pronounced [g], C when pronounced [k] and R ([ɹ], or [ɻ],), T ([t]) don't quite fit in there and I don't know why S and Z occur twice in the row.
    They are not all frictavices since [t] is a plosive, [dʒ] is an affricacte, [ks] is a velar plosive + alveolar fricative, and [ɹ], [ɻ] are approximants
  • This is a really nice insight and exactly what I was looking for, very interesting :) Feb 7, 2017 at 18:09

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