Having someone else suggest the idea will probably take you to places you haven't been before.
For the pro and semi-pro, this is just routine. If you're not, then maybe you don't know what it feels like to have deadline and direction from someone else regarding your music. It's odd at first and may take some time and a few attempts to get used to.
No Failure
Assuming you've not entered into anything contractual, then at worst, the output will be unfinished or bad. You won't have failed, but instead you'll have learnt that you need to change the way you do things in order to achieve what you want. You may also have learnt the current limits of your knowledge and capabilities. That alone is worthwhile. Especially if you can learn it before you end up in contractual situations.
If it works out nicely, then you'll have produced exactly what was required of you or better still, you may have surpassed their expectations. Having the skill of understanding requirements and producing results to suit is again valuable.
Ask Others
Jeff Yates, over on his Facebook page, has taken the approach of asking for fans to name the title of his next song. I'm hoping he gets a serious response, he's a good songwriter and deserves a worthy subject to write about. I think today's the last day for responses and the voting starts tomorrow.
Part of a series by Award Sounds offering a selection of creative ideas to kick-start or rejuvenate a composition.