It's my favourite shop in Rome, but maybe just because music is such a big part of my life. This shop is great because you can find anything you are looking for and for a very good price. Very very well specialized in alternative music. You can find pop music everywhere, this is absolutely the best shop to buy any other kind.
What to buy: This is not something about Rome in particular. Just it's a good chance to buy music for a good price. Pay attention to special prices, discounts are very common here.
What to pay: It depends on what you are buying and if it's special price or not, but you will surely pay less here than in other shops.
I find that my baby loves music, especially children singing. SInce I was a child I have watched Lo Zecchino D'Oro , a childrens' singing contest, on RAI. While in Rome I decided I wanted to pick up the latest CD and I found it in a music shop in Trastevere. It was near S. Maria in Trastevere.
What to buy: Italian CDs
What to pay: Average price for the 2CD set was 20 Euro, I think. I also bought Zucchero's latest, Shake, which was only 10 Euro.