It seems you missed the attachment. The system is a bit stupid, you have to first select the file with the Browse button but then also hit the Add File button.

Yeah, I don't expect people to drop everything and start working on the Lisa... it's been waiting 40 years, can wait a few more! I'll try to experiment myself a bit within limited capabilities. I'll be refreshing the thread with progress.

Ray Arachelian is working on fixing the emulator; he acknowledged my yesterday's feedback.

Lastly, just a minute ago I tried a crazy idea to simply keep shoving new and new series of 8 bits to the shift register without waiting for the sound to finish like below, and it's working — you can basically keep flooding the shift register without changing its state first in any way. Like this:

        MOVE.W #$20,D6
loader  MOVE.W #$FF,D5          ; load only 1s first, then change pattern with every iteration
pusher  MOVE.B  D5,SHR1(A0)
        MOVE.W  #$00D0,D4       ;set some arbitrary delay constant
ticker  DBF     D4,ticker
        DBF     D5,pusher
        DBF     D6,loader

It didn't choke or anything. Produced weird whizzing sound because we iterated through all possible 8-bit pulse train shapes.

In any case, I'm afraid I won't get around to this any time soon. And first we need to emulator to emulate sound correctly, anyway.

(...) However, from the video it sounds like the upper end is somewhat compressed, ie. the increase in volume is not linear. Could you check that with your oscilloscope?

The increase in voltage looks linear (see attachment), but linear voltage increase does not translate to linear power increase, so probably that's why we hear relatively strong difference between quiet levels, and relatively negligible at the loudest levels.

That's for frequency 440Hz, 50-percent duty cycle, notes at individual volume levels played in quick succession.

Also, I am traveling for the next 10 days so won't be able to test anything on the Lisa. But I'll test when I'm back if needed.

Another approach would be to to set the max shift freq and just rotate patterns of %01010101/%00010001/%01110111/#ff in combination with playing with built-in volume. That way, you can update at a fairly low rate, say a couple thousand hertz. Though I'm not sure if it's possible to achieve frequencies outside the audible range in Lisa.

Edit: You know what might work, too? Treat the sreg as a 1-bit dpcm decoder. There's plenty of RAM so that could be fun.

Another idea is to have the same single voice music as I did on the PET, but modulate the volume with a timer driven rapid changes, like, triangle/saw/pulse, much among the lines of the AY-3-8910 envelope abuse. This approach won't bring the polyphony, but very complex timbres instead.

Either way, a good quality sound emulation is needed to be able to tackle the thing. I'm afraid I haven't seen an actual Lisa at any computer museum here, let alone someone's personal possession. It is even biggest challenge than the PET in this regard.

Yes, we'll definitely need proper sound emulation. Either way I guess you've just signed yourself up for some beta testing if we get around to coding something

In any case yes, the volume gain definitely doesn't sound linear, and I'll do the measurements shortly and post here, good idea.

Also, Ray Arachelian is actively working on fixing the LisaEm based on my feedback, so hopefully soon it will be easier to compose stuff; see here for details https://lisalist2.com/index.php/topic,255.0.html

Also funny how I found your article on the PET very shortly before publishing my video, glad I did because I was able to reference it!

Apple Lisa has a strong cult following but (almost) no demos, so there's a fertile ground and large audience if you ever find time to work in it.

Wow, just started to watch the video before seeing this post. Very interesting, hopefully will find time to give it a go. My list of obscure computer hardware to pay some love and get some sound of it grown a lot lately, though. Wish the days were 128 hours long.

Lisa hardware is relatively rare, but there is a good emulator https://lisaem.sunder.net; problem is that it does not support sound correctly yet, but its author is actively working to fix it. Once fixed, I hope skilled people will start coding a lot more for that platform, and explore its sound peculiarities.

For now I had to test all the experiments on a physical machine. I hope with this post to excite others about this platform for which (from what I know) the demoscene is almost non-existent. Except for one Requiem demo which, however, has very simple sound only.

The video is here: https://youtu.be/zKRgtbadZ_U
There's also an accompanying article here: http://forgottencomputer.com/retro/sound/#applelisa