One of the main ICs located on the board turns out to be H8S/2350 microcontroller.
Taken from the website of Renesas Technology.

“The H8S/2350 Group is a group of high-performance microcontrollers with the internal 32-bit H8S/2000 CPU core, and a set of on-chip supporting functions required for system configuration.

The H8S/2000 CPU can execute basic instructions in one state, and is provided with sixteen 16-bit general registers with a 32-bit internal configuration, and a concise and optimized instruction set. The CPU can handle a 16 Mbyte linear address space (architecturally 4 Gbytes). Programs based on the high-level language C can also be run efficiently.
The address space is divided into eight areas. The data bus width and access states can be selected for each of these areas, and various kinds of memory can be connected fast and easily.
On-chip memory consists of large-capacity ROM (H8S/2351 only) and RAM.
On-chip supporting functions include a 16-bit timer pulse unit (TPU), programmable pulse generator (PPG), watchdog timer (WDT), serial communication interface (SCI), A/D converter, D/A converter, and I/O ports.
In addition, an on-chip DMA controller (DMAC) and data transfer controller (DTC) are provided, enabling high-speed data transfer without CPU intervention.
Use of the H8S/2350 Group enables easy implementation of compact, high-performance systems capable of processing large volumes of data.”

C language with a serial interface, now we are talking!
From further reading it seems like this chip is perfect for music applications. However for some interesting bedtime reading refer to the full Chip Document located Here.