I have a FLAC rip of said OST, which I downloaded a few years ago. The FLACs are 44100 Hz, so I'm assuming the CDs were the same, unless some n00b actually ripped the USF set, converted to FLAC with the same time tags, and "upsampled" to 44100 Hz and passed it off as the OST?
All CDDA (Compact Disc Digital Audio) discs are 44100 Hz, FYI. It's kind of part of the spec... It would have been upsampled if needed, so there isn't really any way to tell.
Like most N64 soundtracks (Perfect Dark, Conker's Bad Fur Day), it's been re-sampled to 44100 Hz using Cubic Interpolation.
This is clearly evident in viewing the OST via spectrum analyzer. By resampling the usf using Cubic at 44100 Hz you get the exact same result as the OST. Though, this isn't really a bad thing.
I'm not exactly sure how they used Cubic, but it seems to be more precise then just a general resample using standard Cubic resample algorithm.
I noticed the reverb deal with the Super Mario 64 OST. Some of the reverb methods on the N64 weren't very good, which gives off kind of a bouncy effect. Adding a low pass filter to the feedback made the music sound like it was recorded in a bathroom. It would make sense that the reverb on the OST would sound better.
Interpolation...I don't think so. The Conker OST has obvious higher frequencies than the N64 version. I guess it depends on whether or not the composer decides to master the soundtrack at a higher frequency such as 32kHz or 44kHz before it is sent to be manufactured.
Nintendo EAD games on the N64 never used reverb IIRC. It's just some special delay panning effect (Like OoT/MM). All Rare games used reverb though.
Yes, it was re-sampled using interpolation is what I meant. As I mentioned, you can see this if you take a usf recording, set it to Cubic and resample it to 44100Hz and compare with the ost.