What you stated is exactly why Christina is using a vocal coach, I don't know if she was using one prior but she had her tour this past year and is planning to release a new album. Christina does strain and tends to have her bad moments when she goes and throws in a bunch of over the top adlibs, but the girl can sing. Vocal tone, Christina>BoA. Imo of course.
All of 2AM, Lim Jeong Hee, Kim Tae Woo are considered great vocalists reining from JYP, and IVY
is definitely one of the best female soloists (alongside BoA) who can actually dance and sing at the same time.
And why does the fact that Sun Ye doesn't rank within the top 5 current girl group members matter? Idol groups aren't known for their vocal ability.I'll give it Tae Yeon from SNSD and Hyorin from Sistar, but the rest of the girls within those idol groups are mediocre and plain bad.
My main issue with BoA is that she doesn't sing with an open throat so her notes tend to fall flat or go off key (I mean... I can make a compilation of it if you really want me to LOL) I've stated this thousands of times but BoA's vocal tone was significantly better when she was younger.I absolutely loved her voice then.
Anyways... worst news, BoA's getting a lot of flack for the G.A.B song:
So on topic - it's too bad that the song isn't being well received but oh well. Infinity Challenge isn't really about serious music ventures anyway, it's just about having fun.
Off topic about vocals - as someone with vocal training I can tell you right now that Christina does not just have bad moments, she has had a bad career of vocalising from beginning to now. Vocal tone is irrelevant, it has nothing to do with technique. The thing about Christina is that she even strains on notes that should be easy for her to hit.
The people in JYP you mentioned are considered great vocalists by the general public but in reality are decent or okay at best, in 2AM it's only Changmin. Their support is fine, while their mix might be a bit unbalanced, they could be nasal etc. but the way they sing within a serviceable range is not going to damage their voice. Which is exactly the same as BoA.
About Sunye, I was just trying to make a point about the half air half sound thing. If that's the prefect technique then surely the best vocalist they have must be leagues ahead of her competition. When in reality she is behind Ailee, Hyorin, Taeyeon, Luna and Eunji. I honestly just got annoyed with JYP on kpop star lol. At least BoA showed Park Jimin she needed to stop singing in her throat.
You are right that BoA does not always sing with a completely open throat. She can but she is inconsistent with it. The important thing is that her current skill level lets her belt comfortably up to about C#5/D5 which is good, but beyond that is a hit or miss. I have a feeling that compilation would be full of E5s, F5s or the G5 from Lose Your Mind ><* lol. Trust me when I say that her new songs don't force her out of her current comfort zone. They are however making her get used to the upper part of her comfortable range, so she should be able to widen it with time.