Help with velocity settings on an old PA9 file

I'm starting a potentially dubious task of attempting to resurrect some files from an old Pro Audio 9 archive I have. This and similar archives are the final mix downs (but not bun files) that I made prior to burning a couple of CDs -- this would have been back in 2001 or so. Way back there. Back when photographers were still using film and DAW users had racks of synth modules. Yep, I had my share.
 
This file is 100% MIDI and it loaded fine into SPlat, although it couldn't find its accompanying audio file. But I wasn't worried overly about that. After a moment where I configured TTS-1 for the MIDI chores, I gave a listen. Geez, not bad, really. But in this one file's instance, the bass is way too quiet. I am getting particularly stumped over why I can't get any more volume out of the bass track than I can. I've checked the notes' velocities -- and they're 124 throughout, so plenty of volume there. I've checked both the volume and velocity controls in the piano roll. I've even gone to the Clip Automation (Velocity) and Automation (Volume) controls at the track, yet I still can't get much volume to speak of out of that track. Just to make sure I wasn't imagining things, I copied a couple measures of this track's music to another track that is behaving normally, and they pegged the meter, so I know it wasn't anything intrinsically quiet about the MIDI patch I'd selected. I even tried the reverse -- copying a segment from the track behaving normally to the track that's too quiet, and the segment I copied was playing back quietly, even though I have its velocities set high as well. And I double checked the piano roll for this new segment, and yep they're reading high.
 
This annoying problem is potentially important. I have another 15 files to go through and I figure chances are I'm likely to run into this problem, or something similar with at least one of the other files.
 
I know this is probably something simple I've overlooked -- it usually always is -- but I'm stumped once again. Anyone care to weigh in on this one?
 
UPDATE: I just got this bright idea --- why not just copy over all the note data to a new MIDI track, set it for the preferred voice and preferred volumes and zip, zap, bingo, I'll be done. Welp, it was encouraging for the first couple of measures, and then even odder stuff started happening. I was getting total drop outs, and then the volume would be back, and then a drop out again. Toward the end of the piece, the volume had mostly dropped out for good. So I went back and checked if any of the suddenly silent notes had lost velocities, but nope, they're all still at 124. Looked at the piano roll volume and velocity and everything looks good there too. This is getting curiouser and curiouser. Hey if I have to rewrite the whole damn file again from scratch to defeat this problem I will. Heh. It's just MIDI after all. Why should it be so complicated?
 

msmcleod, thanks very much for this tip. I'd never used the Media Browser in this fashion before. And it's worked like a charm so far. Volume problems with the bass are solved and nothing else seems to be reaching up to bite me from behind, so I'm confident. Working my way through the file as I type this, in fact.
 
You know, there's something to be said for all of those old hardware synths. There are a few voices I miss and can't yet find good replacements for. The quest must go on.