There are several DRM enabled delivery methods available in current and future phones. One to mention: OMA DRM.
Phone can receive many different content types over MMS, XMF sounds, MIDI, SP-MIDI and so on. Whether the device is able to forward that content depends on how it was originally received and if it was set to "forward lock" tag.
Latest devices that has OMA DRM implemented, content with audio/midi MIME type for example can be forwarded, but if audio/sp-midi is used then user can't send it further. Have a look to our DRM documentation about difference capabilities.