To most humans, a conversation between Planetary Citizens is completely unintelligible. The parts that are in the audible range to humans sounds a bit like a chorus of teakettles and small birds backed by a broken fan, or ultrasonic bagpipes. Citizens have two sets of vocal cords, and equate lower pitched noises that travel farther than ultrasonics as shouting. (Humans sound like they're underwater and SPEAKING IN ALL capital letters.)
Communication in the other direction is somewhat easier - Citizens can pronounce most human languages. They have a tendency to sound like parrots in helium rich enclosures or cartoon characters when doing so however. Furthermore, there tend to be a lot of miscomunications when doing this, in part because they often lack the education, and because their speaking patterns are a bit different from humans.
Citizen speech follows a object-adjective-action-adverb pattern, with tone affecting meaning of many descriptions. For example, a human speaking English would say. "Robin is quickly reading her blue book " A citizen would render the scentence:
"The Book that is blue and belongs(owned) to Robin is being read(quickly) by Robin."
The parenthetical areas are where tone makes a difference. A rising, flat, or dropping tone on belongs can alternately mean "owned by", "In possession of" (borrowed/stolen), or "Intellectual Property of" (she is reading the book she wrote). Quickly could be "Hap-haphazardly", "Fast", or "With all due haste" (Only what matters/emergency response)
Fortunately, the Citizens have developed translation computers to simplify communication. However, this still faces a number of problems. Many things like nation or family names simply don't have an applicable translation or pronunciation - which in turn is why most humans have no idea how many families or groups are present. Furthermore, it depends on how much contact the particular group has had with humans. The more aggressive ones may have only commands and taunts, while others can hold long conversations with fail few interruptions from gaps in the dictionary.
The PC alphabet is at both simple and complex, and comparable to musical notation. Letters are a three high and two wide arrangement of lines and dots on a grid 7x2 grid. Standard emphasis is written in the middle, while changes of tone (and thus meaning) are indicated by shifting the letter up or down two rows. Most standard writing surfaces are broken into appropriate grids with spaces in between, and failing that, an unbroken line is drawn through the grid.
Example of standard emphases three letter verb, followed by two letter rising tone adverb:
.. ..There is also a shorthand script composed of pictograms that can be rendered in only one or two strokes. Usually, these are commands and warnings (Stop, Caution, etc.) though it can also apply to very common terms (Food, Store, Walk) or some concept that has earned the right (Space Travel, Famous Individuals, Nations).
l l .l - / / _ _ - ..l . . _ _l . - . .
A citizens individual name is a short signature whistle or chord, with an attached number indicating birth order. so for example G#G#BCb-8 is G-sharp, G-sharp, B, C-flat the 8th. However, their full name accounts for their occupation, matriarchal family name, and nation. So for a full example:
Shipwright G#G#BCb-8 (of the family) x'k-LA (in the nation of) Ozensosk
Not surprisingly, those that spend much time with humans adopt alternate names for convenience and communicability.
Citizens that have established themselves as somehow special - a single birth (quite rare), war hero, great leader, etc. - can earn a single descriptive name like "Iron Dream" or "Blue Princes".