Change sound level when using earphones with iPhone dock When using Music on iPhone the user is able to use a slider to change the audio output level.

However, when the iPhone is docked in the official Apple dock, using the earphone jack in the back, the slider to change audio level is removed from the interface.

I would prefer to use the docks audio jack as it keeps the earphone wire on the surface of the desk rather than floating out the top of the phone over a keyboard and getting in the way.

Is there a way to make the audio level changeable when the iPhone is docked in the official iPhone dock?
The short answer is "no". 

Although it shares a connector type with headphones, the 1/8" mini stereo jack on the Apple iPhone dock is a line-level audio output. Its purpose is to connect the iPhone line out (part of the dock connector) to devices like amplified speakers, stereo amplifiers, etc. These devices provide their own volume control and (aside from fine-tuning of input levels) the assumption is that you don't want to have control over the sound level in two places.