Actually, Shadorne, there is no bass viol on the recording. But, after listening to the track again, it might be a bass trombone, and it does, indeed, read lower than 36 Hz in my room.
Bass Trombone won't go below about 60 Hz, as I recall David Finck plays Bass Viol on this track while Dave Taylor is bass trombone. I can distinctly hear both the bass trombone and the bass viol clearly on my system. The decay on the stringed instrument is characteristically much longer than the bass trombone (wind). They do play only two notes together at the start of Bella Cubana exactly at the same time...but the Bass Viol is an octave lower... (for those who may be confused Bass Viol is the orchestral name for the more commonly named double bass)
Sorry to be a stickler, I may have digital tin ears or don't know how to listen as the Vinyl Analog folks would say, but I hear this all to clearly....