The only way to get the music from iPhone 6 to your computer is through iTunes. Install iTunes, connect the iPhone 6, and browse the Music category. Select the tracks you want to copy using CTRL or Shift, then drag them on your desktop. It's better to create a folder first and then drag the files to the that folder.
You can't move the files from iPhone to Android without an application. I recommend connecting to a WiFi network, then install Dropbox or Google Drive on both devices and upload the music from iPhone to your cloud account, and then download the files to Android or connect the Android tablet to PC through a microUSB cable and transfer the files through Mass Storage (My Computer).