Fran.... Just as it is only a small percentage of arranger purchasers that are pros, so is the percentage of WS buyers. And also, the percentage of TOTL arrangers is small, compared to the whole market. While a TOTL arranger, Fran, CAN be used at a 'pro' level, sadly, the feature set and overall sound is not contemporary enough for young 'pros' to really accept them. Yes, they are great 'meat and potatoes' keyboards, but the sounds?
If I was primarily doing Usher, or Madonna, or Beyonce or Maroon Five, I wouldn't be using my G70. I'd have a MotifXS or a Triton or a Fantom... And trust me... the learning curve to perform well on those things is JUST as steep as an arranger. More so, in fact. That's why I use an arranger - it's easier, not harder!
No, arrangers are not used by younger players because they play younger music. And arrangers are voiced and styled for YESTERDAY'S music. Even the dance and trance styles on a TOTL arranger are at least ten years old. And ten year old styles and sounds don't pack a dancefloor of young kids. Not compared to cutting edge dance loops and sounds that modern WS's carry.
BTW, before you say that young pros won't pay arranger prices, consider the K2600's and Korg Oasys's that you see on stage all the time. Both at LEAST as costly as a T3 or PA2Xpro... (which are also niche arrangers that few of us, even, own due to the cost, and hard to find to try out - heck, even WE have to drive hundreds of miles to try these things out... you can hardly blame the kids for being unfamiliar with them
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Young kids are not stupid... they know what suits THEIR music. It is arranger manufacturers that are stupid, if they think their product appeals to younger buyers. Either they make the investment, and the market grows, or it's 'move over, Home Organ'...