............from somewhere around 1981/82 is a lovely listen. No idea if its easily available (but then again more or less everything is available) and worth tracking down.

If you like jazz, could I recommend Keith Jarrett, especially the solo piano CDs: 'Vienna Concert' and 'La Scala'. (This is about 0.1% of Jarrett's output, though - there's a thread somewhere where Jarrett came up and duco01 in particular pitched in with a superb list....here we go, scroll down a bit...)

http://www.wordmagazine.co.uk/content/ever-been-long-changed-a-band

I recommend those two because I think that you might find them ok to read by - some of the other solo stuff is perhaps more demanding/emotional ('Testament'), and the jazz trio material is awesome but perhaps too 'foreground' for your brief.

Other possibilities might be Mulatu Astatke (there's a best of compilation and a new album 'Mulatu Steps Ahead' on Strut Records) - Ethiopian jazz, basically:

This is some of the most restful instrumental music I've ever heard:

Both the albums they made together ('In the Heart of the Moon' and 'Ali and Toumani') are lovely, although the odd bit of speech or vocal appears in the odd track here and there.

Instrumental reggae could be another way to go - I've had hours of pleasure from the Trojan Instrumentals 3CD box set and the 2 volumes of Sound Dimension tracks (SD were the Studio One house band) on Soul Jazz records, Jamaica Soul Shake and Mojo Rocksteady Beat.

http://www.souljazzrecords.co.uk/releases/?id=4950

but, as a preference, Thursday Afternoon. It's barely there until you really listen to it then it's complexity opens up to you.

Jonsi & Alex's Riceboy Sleeps is lovely reading music. Try Eno's Music For Airports, obviously, and Aphex Twin's Selected Ambient Works 2. The Tired Sounds Of Stars Of The Lid works a treat too.

Bowie's Low has never yet let me down.

Daniel Lanois belladonna
Harold Budd the room
Chopin nocturnes

to being slightly averse to the notion of background music. To me that would be something like Dido or The Lighthouse Family which has no soul or imagination and is literally aural wallpaper.

But I do know what you mean and so I would recommend any of the samplers on the Windham Hill label which are specifically designed to create a sense of calmness.

Or - this may sound weird - but have you thought about recordings of either birdsong or ocean waves or streams/rivers? I have these on from time to time and I find them immensely relaxing.

of the later 50s is perfect to absorb as a background and to listen to carefully. Cookin', Relaxin', Workin', Steamin' are all equally good

This is an interesting thread to me because it may explain why I've never been a book reader. I find it hard to concentrate in silence and I've never really got on with any sort of music without singing (and therefore words). The last time I subjected myself to prolonged instrumental music was when I was revising for finals when I borrowed stuff like Mike Oldfield albums - never again.

Marconi Union - just released on CD;

I can read a book - or a blog, for that matter - quite happily with music going on. I can even sing the song whilst doing so. My wife can't. An odd multi-tasking skill supposedly beyond men.

For lyric-free enjoyment, I rely upon Tangeringe Dream. Tinariwen as well. If I can't understand the words, it counts as lyric-free in my book.

Which, I suppose, brings in the Manic Street Preachers and Napalm Death.