but was it Jacobs who played the tenor tuba solo on the 1977 recording of the Bydlo solo under the direction of Giulini and the Chicago Symphony Orchestra?
I assume it is but I just want to be 100% positive

Here is my source regarding John Taylor and his recollection of AJ using the Bb side for the high C#s. It had nothing to do with Ron Bishop or the high G#s. I'm not sure what quote you're referring to, Ken.Ken Herrick wrote:Two points:
1. The quote about the high G# is attributed to Ron Bishop on p37 of "Song and Wind"..
You obviously had a much closer relationship with Mr. Jacobs than I did (I was a student of his at NU for two years). According to Song and Wind, and my ears, Mr. Jacobs is performing Bydlo on the 1967 Ozawa recording. The timbre seems to me to clearly be a tuba and not a euphonium. Also, the style is unmistakably Jakes, especially the characteristic slight punching of the notes that, for lack of a better term, I have always called the "Jacobs Bounce."Ken Herrick wrote:Todd, Thanks for posting that item by John Taylor, a good one, which I have read previously. What we have here are two quotes about the Kubelik recording with slight variations, ie C# & G#. I recall discussing Bydlo, and that recording with Jake at the lesson when I took my 5v Alex which I had just acquired, used, from, as I recall, Dan Corrigan. So, while I have never "published" you now effectively have 3 quotes about the instrument used not being the York and I definitely got the info from the man himself.
Jake was not 100% happy with the tuning as it came out on the recording saying it had been very difficult to hear others. (Something he often commented on as being due to the quirks of the Orchestra hall acoustics.)
As I mentioned, my "recollection" of the Ozawa recording is that it would have been Glen Dodson on Eupho though I'm sure Jake would have done a beautiful job on the Alex.
Back to John's article, I know of a time when Jake was beaten to the draw at getting the wallet out. Midwest '66 when Harvey paid the tab at Berghoff's for dinner and a LOT of steins for a party including myself, Jake, Harvey, Bill Bell, Rex Conner, Oscar from Mienl Weston, and a couple others. To say that was a priviledged moment to share with those greats would be an understatement!