My MIDI equipment is roughly 30 years old. Here's what I know. My Kawai K1-II synth denotes MIDI note #60 as C3. My Alesis SR-16 denotes MIDI note #60 as C3. When I say "denotes" I mean in both the user manual, and on the instrument's display panel.
Now for the reveal. My sequencer is Cakewalk Pro Audio and after recording MIDI output generated from both the Kawai and the Alesis, Middle C appeared (in Cakewalk) to be C5. This confused me. So after much searching in the Cakewalk help system, I found a general global option named Base Octave for Pitches
which was defaulting to 0. This option controls the octave value, like the 6 in "Db6". So by defaulting to 0, the lowest MIDI note (note #0, which is a C) is visually
displayed as "C0", and consequently visually displays note #60 as C5.
So in order to adjust my software sequencer (Cakewalk) to match the octave values for my instruments, I had to set the Base Octave for Pitches
value to -2. Now when I "see" note #60, it displays as C3 in the sequencer, like all my instruments do. Again it only affects what I see in the Cakewalk Sequencer. It does not
alter the underlying MIDI note number.
Note the Cakewalk help system mentions the Yamaha FB-01 as an example which uses MIDI note 0 as C-2.
I hope this helps someone.
Other ancient hardware like my 360 Systems Professional Midi Bass, also denotes MIDI note #0 as C-2, and hence note #60 as C3.