To copy music from your iPod, connect it to your PC with auto-sync or auto transfer disabled, find and open the iPod's removable disk folder in My Computer, reveal the hidden folders, open the folder named iPod_Control or iTunes_Control, and copy the Music folder from it to your computer. Avoid syncing of the device until all the songs have been transferred to prevent permanent loss of data from your device.
To bypass auto-sync while connecting the iPod to your computer, hold down Shift+CTRL on your keyboard until the iPod is shown in the Source list under iTunes devices. To reveal hidden folders, click on the View tab and check the checkbox called Hidden items.
You can also copy music to your PC using the iExplorer. First, open iExplorer, and connect your device to your PC. If iTunes prompts you to sync your device, click No or Cancel. Avoid syncing your device until all the music has been transferred back to iTunes.
After the device is connected, open iExplorer, and select Music from the Media Library tab in the sidebar on the left. Choose the songs that you want to copy, click on the Transfer From button at the bottom of the Media Library, and choose Transfer Selected to Folder. In the dialog box that opens, choose a folder, and click OK to begin transferring your songs to your PC.