MTV Music Generator (known as Music 2000 internationally) is what got me started making music back when I was young. It's a pretty basic tracker that's very easy to learn, and it comes with an extensive library of pre-packaged sounds to work with. I find a lot of the default melodic sounds to be pretty cheesy, but the drum presets are very usable and given that the 2MB RAM bottleneck of the PS1 often prevents you from getting too crazy with song creation anyway, you're usually better off just keeping it simple with drum tracks. The ability to rip custom samples from CD and store them on your PS1 memory card vastly expanded its versatility, although I still mostly used the limited sample memory for drum sounds. Before I finally shelled out for a drum machine I frequently used the game as a rhythm section on several demos, but without MIDI sync functionality it's little more than a fun oddity to fiddle with every now and then.
I think the PS1 supports some flavor of MIDI sequencing natively through its sound processing chipset, but I'm equal parts confused and intrigued by this YouTube video from 2010. It seems to demonstrate some preliminary form of MIDI sync coming out of a PSX running Music (the prequel to Music 2000/MTVMG). I tried contacting the channel to ask more questions but his account has been inactive for four years now so I don't expect to hear anything from him. He seems to be in to chiptunes from his other videos though, so if anyone knows who he is (or if he has an account on here) I would love to get in touch with him and ask him more about the project.
From what I've gathered reading his replies to comments on the video, it seems as though whatever MIDI sync mod demonstrated in the video is not being achieved through a sound sync workaround. That would require him to send a lone timing pulse through one of the L or R channels to generate MIDI clock while all the other sounds would be forced onto a single mono RCA out, which is a less than ideal solution. Mono out is often the best you can get in the chiptunes world, but sound sync tends to be unreliable anyway and having access to stereo panning and effects is always preferable.
In the comments he further explains that the MIDI output is being sent through some kind of external adapter that he built himself. He had plans to update it to work with MTV Music Generator and then build the adapter into the PS1 itself, but alas, that never panned out. I know next to nothing about PS1 modding, but I'm fairly certain he's not using a modded version of Music because modded PS1 games basically don't exist. It's more likely that he's taking the timing messages straight from a pin on the SPU or the CPU and using this adapter to translate them into MIDI clock, but again, I don't know jack about the PS1 and this is just my best guess.
Anyone familiar with PS1 modding care to add their two cents here? I think this could be a really cool project if developed further and I would be happy to help however I can. Chiptunes purists will probably turn their noses up at the concept of modern PCM sampling in their set-up, but if you're like me and you've always found most of the noise channel and FM drum options within the common chiptunes platforms to be unsatisfying, this could be a neat compromise to get some nice beats and samples into your set-up without sacrificing the vintage aesthetic by using a laptop or a more modern drum machine. The PS1 is old enough to legally drink now, so it's probably old enough to score you at least some street cred. Plus you can use the horrendous video creation mode to make totally not at all cool visualizations for your SICK NASTY beats.