Pink Floyd recorded a session at the BBC's Paris Theatre on September 30th, 1971, for broadcast on October 12th that year as part of John Peel's radio show. It was a wonderful, evocative session, consisting of some of their in-concert favourites at the time. Embryo, Blues, Fat Old Sun,  One of These Days and Echoes were committed to tape, and the last of these tracks, in a 28 minute version, can be listened to (within the UK only, we're sorry to say) for the next three days on demand.

Aired on the Chris Hawkins radio show on BBC Radio 6 Music, you can catch it via the BBC iPlayer service. You'll need to wait (or skip forward) to around the three-and-a-half hour point to hear Echoes. Our thanks to James McGreevy for the info.

UPDATE: It seems certain European countries also have the ability to hear this, in particular Switzerland, so if you are outside the UK, it's worth a try!