Time to get the rumor mill kicked into high gear: Multiple music industry sources say Apple executives have told them the company is planning one of its famed keynote events for the week of Sept. 7.

But in true Apple fashion, the company has been noncommittal about the exact date of the event and what it will be showing off.

I’ve asked Apple for comment and will report back if the company responds. But the timing makes sense and shouldn’t come as a surprise since Apple (AAPL) has traditionally used the week following Labor Day to show off new products and refresh existing product lines.

Two years ago, for instance, Apple introduced the iPod touch, which has since become a key part of the company’s arsenal. Last year, the event featured less substantial changes, like an overhaul of the iPod Nano.

Given that Apple has tipped off music industry executives, it’s a fair bet that the event will incorporate music in some way. Perhaps it will show off the new “Cocktail” format that Apple has been working on, which bundles full-length albums with other goodies like album covers and interactive bells and whistles.

But unless Apple unveils its so-called iTablet, a touchscreen device that’s supposed to be a cross between an iPhone and a full-fledged MacBook laptop computer, there are going to be a lot of disappointed Apple acolytes.

The other big appearance the Apple faithful will be looking for will be Apple CEO Steve Jobs, who hasn’t made an official public appearance since a keynote presentation last October.