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SNES tuning issues
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Author:  lazygecko [ Wed Oct 15, 2014 5:46 am ]
Post subject:  SNES tuning issues

Howdy

I've been digging deeper into SNES music and the workings of the SPC chip lately, and one thing I'm noticing a lot now that I didn't years ago was the widespread amount of tuning problems in lots of soundtracks. Now, for lots of them I think I know what the problem is at least: short samples that loop so fast that they start shifting the frequency after the attack. This is especially prominent in early era Capcom games such as Final Fight and Street Fighter 2.

There's something else I can't quite put my finger on however. In some music it's just certain notes that are out of tune while others play fine. I've noticed this in the overworld music for A Link to the Past, and Simon's Theme in Castlevania 4 to name a few. I don't really know what kind of internal tools they used to create the music and in what manner they input notes, but I kinda doubt that this is just a human error on the composer's part. Could it be some kind of issue with the resampling or something? Possibly this might even be an emulation issue for all I know. But I would need some recordings from real SNES hardware to reference with.

Would be grateful if some tech-savy people here could provide some answers.

Author:  blitzlunar [ Wed Nov 05, 2014 9:47 am ]
Post subject:  Re: SNES tuning issues

The player you're using could be to blame, depending on what you're using. The loop point on a sample (sound) need only be incorrect by one sample (value) and it can cause noticeable pitch issues. Have to admit I've never noticed that problem with A Link to the Past (listening now), though it could just be because I'm so used to the music. As for Capcom, I always found their sound implementation a bit lacklustre, so could believe that the problem is on their end in those cases.

Try some other players, perhaps.

Author:  lazygecko [ Fri Mar 17, 2017 5:14 pm ]
Post subject:  Re: SNES tuning issues

Been a couple of years now, but relatively recently I think I finally deduced why some songs seem to have tuning issues but only at certain pitches. When I looked closer at one instance it was a flute sample, and the volume fluctuations from that in conjunction with the loop appears to be producing some type of amplitude modulation phenomenom once the loop goes faster at higher frequencies, and this in turn yields extra inharmonic content.

Author:  KungFuFurby [ Fri Mar 17, 2017 5:52 pm ]
Post subject:  Re: SNES tuning issues

I looked up one of the sound drivers to see how it handled tuning... it has a fine tune command of sorts, but all it does is simply add the number to a number pre-calculated from a pitch table (before doing any shifting... if this were done after shifting, then it would result in a lot of trouble at lower pitches). This means that the higher the value, the more uneven the tuning between notes.

Author:  lazygecko [ Sat Mar 18, 2017 6:27 am ]
Post subject:  Re: SNES tuning issues

That's very interesting. Which driver in particular was that? You think that particular issue could also be found on audio drivers for other systems?

Author:  KungFuFurby [ Sat Mar 18, 2017 8:54 am ]
Post subject:  Re: SNES tuning issues

I'll just simply give you one game name to find this sound driver in. It's the sound driver found in Bonkers.

In theory, yes, this kind of issue can be found in other sound drivers. It would be least noticeable, if at all, if this fine tune value gets sent through a multiplication value first, with the multiplier being applied on a per-note basis (bonus points if they multiply the value by a 16-bit value rather than an 8-bit value, since pitch is 14 bits).

The other kind of tuning issue would be most noticeable at extremely low pitches (which is much less of an issue for my ears than having tuning issue at higher pitches, such as what happens to the NES's 2A03), and that one is a hardware limitation rather than a software limitation.

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