Yes, especially that which was not considered as hymnody at the time-- so it will be stuff that tended not to be considered for inclusion in hymnals. The parallel would be that while there is a ton of BLUEGRASS gospel, very, very little of it gained recognition in churches as suitable for inclusion in books published for congregational use. Now, some of the old black gospel often WAS used in worship, as well as on the performance stage, but I think tended to be transmitted orally in the call-response or basing forms that came out of the spirituals.