Want more data on the digital music market to stoke the argument about whether streaming services are cannibalising CDs and downloads? We got it! Well, The NPD Group has got it, with some new research into US consumers’ music listening habits.

The topline: 96m Americans listened to music on an internet radio or on-demand (streaming) service in the last three months. That’s 50% of overall internet users. 37% listened to Pandora and other internet radio services, while 36% listened on streaming services including YouTube, Spotify, Vevo, Rhapsody, MOG and Rdio.

The angle that’s causing debate today is NPD’s tracking of how much LESS these people are listening to music through more traditional means: AM/FM radio, CDs and music downloads.

Cue Digital Music News running with “Pandora is Cannibalizing CD and MP3 Listening” as its headline, and tying that back into the ongoing row over how much artists get paid from streams on Pandora.

The flipside of this: the radio and streaming services appear to be fuelling discovery, with 64% of their users saying they are rediscovering older music, while 51% are finding new music. “Pandora and other music services are an increasingly important part of the music-discovery process,” says analyst Russ Crupnick.

NPD’s research is solid, but what’s been released publicly is focused on specific data points. There’s a danger in running with those figures to support or disprove wider arguments in the digital music space.

Understanding how Pandora, Spotify and the rest are disrupting traditional music listening (and spending on more than just recorded music) is something of a holy grail for the industry right now, as is figuring out how well these services are doing with their aim of expanding the legal digital music market.