When buying shares of a music asset, buy orders get placed in a queue system. First come, first served. Your buy order will remain pending until there's a match with a sell order at the same price.
You can cancel your order at any time by going to your Portfolio and Orders. Just hit the X in the upper right corner of the order you want to cancel. Why not try another price?
Hint! You can see the price range other investors are willing to buy or sell for in the order depth on each music asset.