It's very nice, you have long phrases and good air control! Most of us would have trouble doing this phrases on a regular bass trombone. You make it sound easy even on a contra! Well done!
Excellent intonation and phrasing. Obviously your playing and technique on this difficult instrument is extraordinary.
As a bass trombone player I frequently play these etudes in all three octaves and in other keys. I enoyed your performances but after many years, I think I like hearing this music in the original tenor trombone range the best. I would also like to hear them performed as they were intended by human vocalists. Is that out there?