Strata East was formed by Charles Tolliver and Stanley Cowell, back in 1971. According to Michael Cuscuna's notes to the Tolliver Mosaic Select the recordings are owned by the artists themselves, so maybe that's the reason why so few have been released on CD. Apart from the Tolliver Mosaic, I have only one Strata East album on CD, Clifford Jordan's Glass Bead Games, which was issued by the Japanese Bomba label.
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See felser's post above for more info