Maybe this can be confirmed by TheSource, but just skimming though the Sinobi site revealed that the pre-orders for Wii Music in Japan aren't anything to write home about.

「しかし、予約状況も含めた市場の反応は渋く、今ひとつ盛り上がって来ない。」

Another odd thing I noticed was that when the Wii ads fired up on TV in Japan last night, I was thoroughly expecting to see heavy Wii Music advertising, but instead just got the same old Wii Fit ad (yes, Wii Fit is very, very heavily pushed in Japan via TV ads).  No Wii Music ad, at least not during that break.

Obviously if the title turns out to be a strong long-term seller then Nintendo will once again be laughing all the way to the bank, but...

It depends, because the type of person that buys Wii Music won't be the type to pre-order it. Thing is it's Japan, and I don't know if they have the same level of casual players over there.

Based on Nintendo records of laughing-to-the-bank, I am betting on that for Wii Music, too.

If they put a schoolgirl holding a triangle on the front it would sell milions.

Sorry I have nothing more intelligent to say.

www man, come on. You would think after these two years that people would understand what's the deal with certain Wii titles. Need i remind you what kind of sales Wii Fit had on it's first week in Japan? What happened next?

Don't you worry a thing about it, if it is meant to sell a notch, it will.

Weren't there like a million pre-orders for too human?

http://www.n4g.com/xbox360/News-181529.aspx

and we know what happend...

I cant read japanese
But I stand by my prediction atleast 10 million units sold in 2 years

Did anyone really expect it to that much of a success?

Why would anyone preorder Wii Music

 Where do people get these numbers anyways? Doesn't anytime someone mentions pre-orders on a national scale it actually means pre-sales to retailers. Because I don't know how anyone could realistically determine how many pre-orders are being sold to consumers accurately in any reasonable time frame. I mean according to the link you posted.

“According to sales reports from Gamestop, EB Games, and Microsoft Co...”

Oh there's three sources I trust for accurate, well collected data, with no bias clouding their judgment. =P

Wii Music will be fine. Like a LOT of Wii games it won't be top heavy and it'll just keep selling steady every week untill years later.