First shot... how to improve?

[clarnibass]

Most of what I do is photos of musical instruments for my website (mnual type for reviews of instruments mostly). Until recently I used my Canon A570IS P&S. I just started using a Canon Kiss X4 (aka 550d, aka T2i) with 18-55mm kit lens. Actually this is my first real short with it.

I'm looking for any info to help improve. I'm still working on trying AV, TV and M modes, figuring out what works best where and when. Here is some info: Photo taken at the small porch of my 2nd floor apartment. Mostly natural light, with no direct sun light, relatively low light at the time, with flash (no flash photos all were too dark). Clarinet lying on white sheet. Camera hand held at slight angle above clarinet. ISO 100, AV mode, f/3.5m, 1/200 shutter.

I took about seven shots. Only one (this one) using flash, was relatively sharp and bright enough. Main issues I think are colours (not sure why the background is so not-white, it's a very white sheet. Also I would rather get rid of some dots on the wood body, but I don't have Photoshop, all I got is a free software I got online. I would like to get rid of the shadow on the right side but had no way to have better light or a way to edit it out. I also didn't have a better way to position the clarinet or hold my camera. So it is what it is.

Any help will be appreciated!

Thank you!

P.S. I can't see an icon for attaching photos so I'm linking it instead.