As a bit of follow-up after reading all the posts in this thread, I did another experiment, which produced the desired result:
NOTION 3 v3.2.9960 ~ Mac OS X 10.7.2 (Lion)(1) I selected the 1st voice for input and entered the notes, followed by making the three sets of notes tuplets . . .
(2) Then I switched to 2nd voice for input and entered its notes, but I was not able to make the 2nd voice notes become tuplets, so I selected, cut, and pasted the 1st voice notes to a new measure, followed by making the three sets of notes for the 2nd voice in the original measure become tuplets, followed by selecting and copying the 2nd voice tuplets in the original measure and then after moving the insertion point past the last 1st voice tuplet in the new measure, I pasted the 2nd voice tuplets . . .
It requires a lot of words to describe the procedure, but it does not take much time to do once you understand the procedure . . .
And I did some experiments where I changed the pitch of notes, and this appears to work with no problems, although it looks a bit odd when the notes of one voice are below or above the notes of another voice, since rather than doing the actual elliptical note portions as if they were a two-note chord, the notes are spaced so that there is no overlap, which probably makes sense, because without color-coded printing it would not be clear which note goes with its respective tuplet . . .
Lots of FUN . . .
P. S. Pianists and keyboard players tend to be vastly annoying, since they nearly always know a
lot about music theory, which is antithetical for a "play by ear" musical group, so my strategy is to find someone who is bright; has a keen sense of rhythm; and is a quick learner but knows nothing about music theory . . .
The next step is to show them the major triads for {C, D, E, F, G, A, B} and the minor triad for A, which covers "Sleepwalk" (Santo & Johnny) and every other slow song, followed by showing them how to do the equivalent of what on guitar I call "chickin' pickin'", where the key is to do it rather than to think about it . . .
Then, they can play the electric piano on songs like this one from the vault of the Surf Whammys golden oldies, which is fabulous . . .
[
NOTE: I got the idea for this style of keyboard playing from the Shea Stadium version of "I'm Down" (Beatles) and the way John Lennon did it, which is hilarious . . . ]
"I'm Down" (Beatles) -- Shea Stadium 1965 -- YouTube music video[
NOTE: The key to this style of electric piano playing is found in the fact that the human mind constantly strives to make sense of chaos, hence if you play a virtual festival of chaotic notes very rapidly the frontal eye fields (FEF) region of the perceptual apparatus in conjunction with the auditory cortex of the human mind will select the subset of notes which sound "good" but otherwise filters or ignores all the "bad" notes . . . ]
"Hey Sugar Britches" (The Surf Whammys) -- MP3Fabulous! 
