I create and modify a lot of the Tyros 4 styles to suit my performance and playing needs. I particularly like adding the CHD 1 (midi channel 12) from the Ethereal Voices style under Movie & Show or replacing the channel to other styles to add that sustained choir sound.
The normal choir voice assigned to this CHD 1 channel is BoysChoirOoh and each Main Variation builds this choir voice up A through D. I noticed when changing this voice, while just normally playing this style or in Style Creator, BoysChoirOoh is found in the Voices (Revoice) Preset Folder.
I was surprised to find this Preset Folder within the Choir folder of the Legacy folder instead of just the main Tyros 4 Choir folder. I found that this Choir folder that contains the Ethereal Voices "BoysChoirOoh" voices has 17 other choir voices within. Each choir voice is either a brand new Tyros 4 voice or reworked voice samples. All 17 sounds sound superb when substituted for the BoysChoirOoh voice. This can add a huge variation to this really outstanding Ethreal Voice style, while totally changing its overall sound.
Odd Yamaha would put 17 brand new choir voices within the so-called Legacy folder. I thought Legacy voices were previous voices from previous Tyros models. Anyway, my point is most of these 17 choir voices would be unnoticed and hidden within this folder. I upgraded to the Tyros4 mainly for the choir and human voice sounds. So if you need a certain choir voice or sound other than from the main Choir folder, check out a few of these - namely "Voices", "Choir", "Air Choir" and several others.
Sorry if I went into too much detail, but it was hard to explain. I hope some of you find this useful.