64MB music cart "A Winner is You"

So it seems that RetroUSB has made a board/mapper to handle a 64MB ROM, and they've used it for a music album by Sergio Elisondo.

RetroUSB product
Video promo from author of music
Video interview with author
There's a look at the board here: Interview video at 4:31

Appears to be CHR-RAM, and has a CPLD for a mapper. Not sure if the RAM is bankable, or how big the PRG banks are.

It doesn't sound like there's anything special going on for compression, since 64MB should easily do 45 minutes of uncompressed 8 bit PCM at reasonable samplerates.

The description page says "Over 20 minutes of music", or about one LP side, and 64 MB for 1200 seconds is 55924 bytes. (At that rate, the player is probably less than one second of audio.) That's higher than the Nyquist rate for RF's practical passband, which is about 32 kHz. So yes, it sounds practical if you can afford 1. that much memory and 2. 99 percent CPU attention to keep feeding samples to $4011.

I guess the next engineering step would be to upgrade from a 1-side EP to a 3-side CD-length album. I estimate that a 4-bit DPCM codec at 32 kHz is practical, which would run for 70 minutes on a 64 MiB storage medium.

In the video you can see that there's no animation at all, so yes it's definitely using full CPU.

So if there is ever another fami compo pico, then with this cart you can put all the best songs on it instead of just the top 10. Also is the 64 mega bit or 64 mega byte?

Could you not put music on it, but just make one super huge NES adventure game?

Famicompo has two original categories: NSF and all-gear. A 70-minute capacity at 128 kbps ADPCM would allow selling a cart with all worthwhile NSF originals and the top several all-gear originals. But then the cart would have to support both the NSF mapper (for bankswitched tunes) and a mapper capable of addressing the whole 64 MB (for all-gear).