For no particular reason I started reading up on the original [AdLib Music Card](https://en.wikipedia.org/wiki/Ad_Lib,_Inc.), and it's clear that this card was little more than a stock [Yamaha YM3812 music chip](https://en.wikipedia.org/wiki/Yamaha_YM3812) (aka OPL2) glued to a PC's 8-bit ISA bus slot. One thing that stood out was that the AdLib/YM3812 chip has two general purpose timers, one with a 80 µs and the other with a 320 µs resolution. However, neither the [data sheet](https://pdf1.alldatasheet.com/datasheet-pdf/view/84281/YAMAHA/YM3812.html) nor any documentation I could find mentioned any proposed or intended uses for these timers.

A few theories:

1. It was included by Yamaha to support features in their digital keyboard lines such as clocking accompaniment rhythms or possibly additional downstream audio processing. In other words, it was wired in by AdLib just because, but with no intended use cases.
2. It was used by music players or games to provide clocking for music playback (similar to generating MIDI ticks) rather than relying on beam counting or some other method for keeping musical time.
3. It was used to provide further modulation of FM generated sounds in software.

What is interesting is that, even though the AdLib card was built with the glue logic, traces, and pin holes to wire the YM3812 timer IRQ line to a PC bus hardware IRQ line, pin headers were apparently never installed and these lines were never connected, thus AdLib was not actually capable of generating hardware interrupts.

Another curious finding was that, according to some [online documentation](http://shipbrook.net/jeff/sb.html), the AdLib "will signal a TIMER interrupt (INT 08)" when the time expires. However, with the IRQ line of the YM3812 [not connected to anything](http://docs.google.com/viewer?a=v&pid=sites&srcid=bWFsaW5vdi5jb218d3d3fGd4OjEwNDEwYzVhYWRkMjAwZDM), I'm not understanding how this is possible. It seems that lacking a way for the card to signal the CPU that its timer has expired would somewhat limit its usefulness.

I'm curious if there were any well-known or common uses for the AdLib's timer. If so, I'd be very curious what historically significant programs, titles, or other out-in-the-open historical source made use of it.