A long time ago I was doing the same research and I went for the TC helicon Voicelive 2. Since then Digitech and TC helicon as put out a bunch of new products. But TC is still worth researching: they have all in one units and some smaller ones for specific needs ;)

I've been doing more research and I spotted the TC-Helicon version of the product with similar spec and rack mounting. The youtube examples looked positive, so I've taken a chance and ordered the TC-Helicon.

I realise that people love making youtube demos of products, but some people really cannot sing, but do!

My next question will be to see if I can get the MIDI in on my S16 stage box to route through to the MIDI out on my X32, which would be brilliant, but I suspect this is not going to be possible.

Congratulation on the TC. As for the midi connections, the s16 doesn't seem to have any. What do you want to control ? the x32 or other gear ?

The S16 has MIDI in and out, as has the X32. My cunning plan is to put the harmoniser out front where the sound man change the programmes, song to song. I don't want to use an analog audio input to control the harmonising, I'd like to control it from the keyboard MIDI out, and the MIDI facility is more responsive - especially if the intro to a song is very quiet compared to the loud bits. I can't find any patching setup that appears to connect the MIDI in on the stage box to the MIDI out on the X32. I was hoping that somewhere there would be a tick box MIDI thru facility. Otherwise, the gizmo will have to be worked by the pianist, who isn't technology comfortable.

EDIT
Bummer! Just had Behringer confirm that the MIDI can't be used to 'bridge' the stage to FoH gap. It's happy sending and receiving program change messages, but there's no data stream of the MIDI data, so on stage it has to be!

Yeah that's what I tought.. sad..

Well - I actually bought a TC-Helicon Voiceworks, and I'm pretty impressed. Looking for stuff to try it on, I found something with a solo voice, and it's a bit exposed, so the MIDI piano track sent to the Voiceworks, the vocal track sent to it as well, and then the Voiceworks output recorded to a new track (and not even in stereo, because I'd used all the cables to hand!). No tweaking, just a preset already set up. I mixed the harmonies rather high so you can hear them. There are a couple of notes in the piano track that confused the harmonies but that would be simple to fix - so, this is probably typical of what you would get live, but I can see me using it in the studio, after this quick experiment.