Playing a song out to my friend while I'm on a call with him/her on an iphone4

Multitasking Scenario:
I make a call to a friend and while I'm on the call. . . I'd like to browse through my music collection on my iphone. . select and play my favorite song to my friend right then & there. Is this possible say on an Iphone 4???
OR. . I'd just like to play out something I recorded using the iphone recorder to a friend while I'm on a call. Is this possible on the iphone 4???. . . .

I tried this on an iphone3Gs and it did not work. . . . . .but I'm able to do this on my nokia 6680 and this is an experience I share a lot with my friends. . . I LOVE THE IPHONE. . .but one of the reasons for me not buying the iphone yet is because I miss this feature.

I don't own an iPhone so there may very well be a solution for this. In the mean time though, you could use this to generate a link to the song on the iTMS and send that to them. They can then listen to a preview and purchase it if they like it.

Sending them a link is not the solution for me. I need to play a song while on the call. . . for me its like an instant preview so we could talk about it on the call itself.

I totally understand the need for this feature. Imagine if John Cussack had to text that girl a link to the song "In your eyes" instead of holding that radio over his head!

Doug