I've attempted a different (and much longer) explanation of the grammatical 
voice suffixes.

MNCL5 "Participles"

MNCL5 non-verb forms are sort of like participles in some other languages, only 
the same general system is used regardless of whether the stem is a verb-, 
adjective-, or noun-type stem. Of course, the noun- and adjective-stem forms 
aren't normally considered participles! They're mentioned below for 
completeness.

There are four types of participles in MNCL5. The 1st is constructed without 
adding any special suffix. The others are constructed with the following 
suffixes:
2nd: -m- suffix
3rd: -t- suffix
4th: -g- suffix

Which of these can occur depends on the word stem's argument structure. 
Whether or not the participle must be preceded by an "object" (in the genitive 
case) also depends on the argument structure.

For reference:

http://qiihoskeh.googlepages.com/M5Morpho.htm

Note 1: It's frequently easier to translate MNCL5 participles using relative 
clauses and this will be done in the examples. Also, don't take the English 
tense too seriously.

Note 2: All example phrases will take the patientive singular ending -a. They 
will typically have the form:

definite-article genitive-object-phrase participle head-noun

Note 3: The 3rd person pronominal roots, z- (3A, animate) and n- (3I, 
inanimate), are also used for the definite article.

1st Participle Only

Most noun stems, most adjective and other static verb stems, and some 
monovalent dynamic verb stems (those with involuntary subjects) have only 
the 1st participle. The verb stem participles are translated as either passive or 
active participles in other languages, depending on the aspect.

zo falo vira -- "the man that fell"
zo fal'yo vira -- "the falling man" (imperfective aspect)
zo fal'ho vira -- "the fallen man" (retrospective aspect)

2nd Participle Only

The remaining monovalent dynamic verb stems have only the 2nd participle. 
These are typically translated as active participles.

zo kor'mo hunda -- "the running dog"

1st and 2nd Participles

This category contains the divalent dynamic verb stems referring to actions. 
Here, the 1st participle is passive (with an object denoting the agent) and the 
2nd participle active (with an object denoting the patient).

zo Jono baito hunda -- "the dog John bit"
zo Jono baitmo hunda -- "the dog that bit John"

1st and 3rd Participles

Most of the remaining divalent dynamic verb stems are here along with the 
remaining noun stems, adjective stems and other static verb stems. For these, 
the 1st participle is active and the 3rd participle is passive.

zo Jono vido hunda -- "the dog that saw John"
zo Jono vid'to hunda -- "the dog John saw"

For noun stems, the object of a 1st participle is typically translated as a 
possessor:

zo viro handa -- "the man's hand"

The 3rd participle could be used like this:

zo ruyo teilto fogla -- "the red-tailed bird"

All Four Participles

Only the trivalent dynamic verb stems use all four participles. The following 
sentence is used for reference:

Zo virak zo cika no librok gebek.
3A-ADJ man-AGT.SG 3A-ADJ child-PAT.SG 3I-ADJ book-THM.SG give-PST
-- "The man gave the child the book."

1st-A) zo zo viro gebo cika -- "the child who the man gave something to"
The 1st participle refers to the recipient and the object to the donor.

1st-B) zo no libro gebo cika -- "the child who was given the book"
Same, but the object refers to what's given. This has to be inferred from the 
semantics of the phrase.

2nd-A) zo zo ciko geb'mo vira -- "the man who gave the child something"
The 2nd participle refers to the donor and the object to the recipient.

2nd-B) zo no libro geb'mo vira -- "the man who gave somebody the book"
Here, the object refers to what's given. Again, semantics are involved.

3rd) no zo ciko geb'to libra -- "the book that was given to the child"
The 3rd participle refers to what's given and the object to the recipient.

4th) no zo viro geb'go libra -- "the book that the man gave"
The 4th participle also refers to what's given, but the object refers to the 
donor.