What I'm going to say next involves a whole lot of links, so you might find it an easier read if you open up a new window for your browser, or a new tab, so you can flick between this page and the new tab or new window, which you keep for the links. Easier than forward/back buttoning.

A 'volume pedal' or an 'expression pedal' are two different names for the same thing. And you can tell if you are looking at one by studying the plug that comes out of it. If it's what's called a 'TRS' plug, there are 3 shiny metal bits at the end, separated by two insulators of black plastic. 3 shiny bits = TRS = volume/expression pedal.

And as mentioned  before about the Roland FP10, a volume pedal, 3 shiny bits (zoom up on it and have a look), it deals in volts, real world. Your Williams keyboard doesn't have a plug for this. It has MIDI instead. Numbers. Needs a translator from volts to MIDI numbers. That's what the Pedal Controller is for.

Now, your keyboard has (should have had) a VERY capable pedal assembly. That should mean it handles what's called 'half pedal'. Have you ever had a real piano? You probably used its pedal as an on-off contraption, stomp the pedal you get Sustain, lift foot and there's none. But you can operate the pedal IN BETWEEN stomp and lift
to CONTROL THE AMOUNT of Sustain you get. Adds to the shades of expression open to you, plenty.

So, choosing the FP10 was aimed straight at that, and the Pedal Controller HAD to follow. But now you know that ANY pedal with a TRS plug will be a volume/expression pedal, so you're a smarter shopper just like that. Sweetwater's no good. Where do you go from here?

ASHBY SOLUTIONS. Run down to the MidiSolutions Pedal Controller. I'll quote from it -

- and the quiet nasty there is a MAJOR nuisance with pedals, which can apparently be fixed just by the Pedal Controller itself - I hadn't known that!

Here's the nasty. Electricity has two directions, positive and negative. Keyboard and pedal makers have NO standardisation on which - and that will include Williams. This situation  leaves shoppers pretty much buying one brand of pedal with nothing but hope for the best as the prospect. 50% of the time the buy will be wrong. Now modern pianos can be built to sense the pedal you happen to have... but I wouldn't count on it with Williams. Plus by and large the pedals which come with switches to flip the volts over aren't TRS.

But with this Pedal Controller it looks as though the nasty is beat. You can buy any TRS pedal, confident.

Run further down the page to see the Deal Plans they offer. Pedal Controller is $125 for the unit, with 2 increments of $15 for their 1-year, 2-year Programming arrangements.

All up, Ashby Solutions looks damn useful. Read what they have to say on their -

HOME PAGE

- where they look made for you. Get on their CONTACT US tab and see.

And if that is still No Go, Midi Solutions itself, a Canadian company, looks as if it will play ball also, programming their Pedal Controller for $20, let alone selling it.

Let's see how that all goes!

ADDED: There's the real world on one hand, and numbers on the other. MIDI  is numbers. What the pedal deals in is volts, real world, and those volts need translating to numbers, else pedal can't talk to piano.

And what the pedal has to talk about is how it's a sustain pedal and here's the number for its position now. If it says anything different, or nothing, you don't get Sustain.

That job, measuring the volts into numbers, then sending a stream of such messages
(Me=sustain, Myposition=number), is what the Controller must be programmed to do. Someone will have to do it for you, and the way of the world is they'll charge for service. Hard to avoid. Thought you might get it as a freebie, but No.

Fix on Sustain-ing and see this is a needed step, like a taxi ride gets you there.

http://www.sweetwater.com/store/detail/DP10
http://www.sweetwater.com/store/detail/MIDIPC/

- put them in your Cart. Next 'Search' for MIDI CABLE, and put that in your Cart.

Pay. Result will be you're assigned a Sales Engineer. Explain things to him (send him a link to the keyboard's manual), ask him will the hookup work and if No, cancel out. Otherwise go ahead. But get him to program the Pedal Controller as necessary - it'll keep the result forever once programmed - and, if he needs a speedup on programming point him to http://midisolutions.com/prodped.htm and http://midisolutions.com/faqs.htm#Programming.

Also, take note of the DP 10 Pedal's problem, (and partial-fix), mentioned http://www.forum-pianoteq.com/viewtopic.php?id=355, posts 1 (and 3 respectively). Those posts were mid-2008. Plenty of time for Roland to hear the howls of complaint and fix the problem. Ask the guy.

That's what I'd do in your place. The piano's well reviewed by users, so though this hookup's not cheap, the outlay seems worth it. Good luck!

ADDED: BTW, if you're quick, notice they've right now got ONE 'demo model' of the second item above (Midi Solutions Pedal Controller) available for some $20 knocked off. Meantime with the standard deal they are 'awaiting stock, some weeks'.

That'll get you fixed for the aims you state.

By the way, there are cables claiming to change USB output to MIDI, and though I've never used one I've seen they're cheap. So a possible linkup should be Sustain pedal with USB-out connected to keyboard MIDI IN via such a cable.  My advice is try it before you buy; but that'd give you more choices with shopping.

ADDED: extremely pressed for time just now so hafta sign off quick, but I don't trust such cables, and MIDI is a dying standard now. Hang fire till I've got more time.

Thanks so much guys you've been a big help already!

ADDED: myself I'd go the MIDI-connected way, simple enough. But there's a missing parts puzzle here, which even the questioner mayn't know the full scope of, and it's likely interaction with Customer Service will fill it in better than I can.

it resembles the old SVHS video connector, but that had 4 signal pins not 6, so it's unlikely your piano will ever hook up to standard parts - meaning it's Williams parts or nothing.

...or a soldering iron and some trial and error

As you look at the pic there, spot the links to User Manual and Assembly Instructions. Get them, they could help you. From the Manual the pedal plug is non-standard, it resembles the old SVHS video connector, but that had 4 signal pins not 6, so it's unlikely your piano will ever hook up to standard parts - meaning it's Williams parts or nothing.

Hit the SUPPORT link at top of the page and there's you'll find lots of helpful links, including Customer Service, Replacement parts, etc. Very interesting is THIS PAGE which gives the Cat. Numbers for pedals and cable, plus board to attach pedals to (if you haven't got that; gotta have something, to hold the pedals stable).

Good luck. Think you'll have it.

Unfortunately I don't want to use Pianoteq but I hope that wont dissuade you from helping me haha.
I want to be able to affect the piano (the one in the link is indeed the one I have) using only the stand
alone pedals without having to plug it into the computer. There is a uher jack for the triple pedals
(will other companies 3 pedal sets work on mine?) and then some Midi Ins and Outs and some Stereos.
I believe there is also a usb connection. Could I hook up just a single sustain pedal through the usb?
Is there such a thing as a usb pedal and will the piano be able to read its signals?

    Thanks once again, sorry I am structuring this like your customer support, but I really really appreciate it!