Q: iPad 2. Cannot download music in iCloud to device.

Hello, Footplate!

Welcome to Apple Support Communities!  From what I'm seeing here in your post, you're having some issues downloading music on your iPad 2, but it's working fine on your iPhone 6.  I can certainly understand wanting to have all your media on all your devices!  I would be happy to help in any way I can.

First, it's important to make sure your iPad has the latest version of iOS software.  From what I found on the Apple security updates page, your iPad 2 should be able to use iOS 9.  These documents will help you back up your iPad and get the latest iOS version:

How to back up your iPhone, iPad, and iPod touch

Update the iOS software on your iPhone, iPad, or iPod touch

Once you're up-to-date, make sure you have enough room in your iPad's storage to download songs.  This article will help with that:

Check the storage on your iPhone, iPad, and iPod touch

It might also be helpful to try a different Wi-Fi network, if you haven't already, as detailed in the "Get more help" section of this document:

 If an iTunes Store purchase unexpectedly stops downloading

Have a fantastic weekend!