If you want to hear songs on your Google Android phone, open up the default player or pull up TuneWiki. If you want to hear songs play on your computer without ever putting down the Google Android phone, get Gmote.
Gmote is a free application that turns your Google Android phone into a remote control to pick, play, and pause music and videos on your Mac or PC. Not to be confused with the Firefox extension gMote ("g" as in "gesture"), this version works in tandem with the Gmote server you install on your computer. When both apps are buzzing on the same WiFi connection, you've got yourself a network that gives you access to your media files from your phone.
Gmote achieves this with two somewhat awkward, but still functional interfaces. The main interface groups the Play, Stop, Skip, and Volume buttons in the center. In the top left there's a button to browse your entire file system for media, and on the top right is a power button that kills the player you've remotely opened.
When you click Browse, Gmote will show you the file path you laid out during setup that will lead to your media. You'll save yourself headache if you create paths to your most-visited folders rather than to the entire C drive.
If you select Touchpad from the context menu, Gmote converts into a remote mouse you control by dragging your finger around the screen. You can use it to open folders and launch your videos and music. Unlike the browsing feature, which presumably is as sensitive to distance as your Wi-Fi is strong, using the touch pad is something clearly done best within visual range. Unlike other remote cursor applications I've seen (I'm thinking specifically of Air Mouse for iPhone,) Gmote's touch-pad movements are slow and jerky, and you can't adjust the sensitivity and speed to your personal style.
There's certainly room for improvement, but Gmote can stand on its own as an app that combines cool factor and utility.
Note: Gmote and other remote apps that rely on Wi-Fi connections to form "networks" between the computer and mobile phone are usually crafted with private Wi-Fi networks in mind. Workarounds to create ad-hoc computer-to-computer networks can be successful, but aren't always.