Shortcuts wouldn't surprise me - honestly speaking - given how ambitious their goals were at the time... Bilinguals - especially the first time through - always sound awkward af or are done lazily to meet deadlines (Yohioloid may be the 1 exception). That's not unique to SeeU.
- Luka English V2 had a lot of missing data (at the time, it was more like a gimmick and made for Japanese users only). V4 had more data, but it was poorly programmed, even for power vocal standards (power vocaloids always have some degree of choppiness, but Luka V4 took the cake)
- Macne Nana... the less said the better. I could use a Japanese library and not tell the difference. That's how accented she is.
- Miku Eng: it's gotten better with V4, but still awkward due to accent issues (r/l/w).
- Dare I mention the bad experiment that was Sonika - and that was a native vocal. Sounds like they tried to experiment with "How cheaply can we make a vocaloid, using a singer that doesn't have access to a studio?" She's not a bilingual, but I do put her in the "ambitious for the time" category. Non-studio vocals have gotten better over time.
I love Miku's English as a native speaker myself (both versions for different reasons- v4 was my first but boy was i happy when my parents helped me buy v3).
I grew to appreciate it more familiarizing myself with more advanced Japanese pronunciation and like, the way the mouth is held and stuff and thus being able to detect elements of Japanese pronunciation in her accent, as well as seeing Japanese people try to speak English. And I realize Saki Fujita must have worked really hard to learn for the project. She had to learn a lot of sounds that were foreign to her and how to properly pronounce them. Miku exaggerates some sounds and pronounces them awkwardly because since Saki's unfamiliar with them, so is she. She was doing the best she could despite not really knowing English. (I also just think her accent is cute tbh lol, and I'm just being a know-it-all)
I think Macne Nana's point was to capture the voicer's natural accent; as a result, however, phoneme editing with her is...certainly an experience. Miku does have some trouble pronouncing Rs but not quite to Nana's extent and it sounds more like an accent thing and less like a
speech impediment...
But yeah, as an L2 Japanese speaker, SeeU Japanese just sounds entirely phonetically Korean, those Rs especially. I dunno if a single JP-EN voicebank reaches "phonetically Japanese" territory other than maybe Nana.
Sonika's a darn shame, because her voice is really sweet and pleasant but her quality is so bad. I would totally get her if she wasn't potentially a total nightmare to mix.
I've tried Luka V2 English and yeah, she's really choppy, isn't she? Her voice is sooo pleasant though. I wish she was easier to use. If I were to choose between the two I'd get V4 to save some pain; in her case I like her but I dislike the Straight/Soft situation (Miku V3 and V4 English are a generation apart but they make a MUCH better XSY pair).
As for my thoughts on how Japanese Vocaloids sound, yeah, they have pretty odd accents for the most part. But hey, that's part of their charm. (There are some pretty naturally-accented Japanese Vocaloids out there though.)
I'm just half Japanese but I can tell that I can understand most of Japanese Vocaloid without lyrics, as long as no weird "tuning" in consonant where shouldn't be, let's say, no extra "n" syllable everywhere (*cough* Kyaami's tuning tuto) made "s" sound extra long with no good reason or stopping of "k/t/p" where shouldn't be.
In Japanese there's difference between "kite/きて" and "kitte/きって" (little "tsu" in this case makes a noticeable small pause between "ki" and "te" unlikely in "kite" which is just continuous) many Oversea users who knows none Japanese often puts that little "tsu" in places where is should NOT be. And it sound WEIRD and UNNATURAL to me. Sometimes people do this is "an accent" purpose but for me it's just... annoying. (IDK where I should compare this but I guess that this is as annoying as someone cannot say "r" in English.)
I am aware of the difference between single and double consonants, but we Western producers generally lower the velocity of consonants for extra impact, like the singer is almost "drawing back" to pronounce the next syllable, like their tongue is a bow and the syllable is an arrow...or something. (I think I've seen Japanese producers do the long consonant thing as well. I wonder if they're mimicking Western producers?) I suppose I could stop doing it but I won't always know how to add more impact to a syllable otherwise.
But something I love about Japanese Vocaloids is how little phoneme editing you have to do aside from velocity edits, silent vowels and stuff to "decorate" the performance (e.g. end breaths and the aforementioned "drawing back", and in Crypton V4X's case EVEC as well if wanted).
Also, since then, there has been Xin Hua Japanese, and I think her accent is more noticeable than Tianyi's. I've heard WIL is voiced by a Filipino as well, I dunno how strong his accent is, I think I hear a bit of Filipino in his voice.