A Deep Dive Into The Sound Of An Apple II

A major part of the retrocomputing scene for many of us lies in the world of chiptunes, music created either using original retrocomputing hardware or in the style of those early synthesiser chips. There’s one machine we don’t hear much about among all this though, and that’s the Apple II. Though probably one of the most expandable of all the 8-bit home computers, it lacked a sound channel beyond a speaker hooked up to a memory location port so any complex sound work had to be done via an add-on card. It’s something [Nicole Branagan] has investigated in depth, as she demonstrates first the buzz from the speaker and then what must have been an object of extreme desire back in the day, a Mockingboard sound card.

Her card is not an original but a modern recreation using the same hardware, which is to say a pair of 6522 VIA port chips, each driving an AY-3-8910 audio chip. This is already a familiar device to those who have heard an Amstrad CPC, a later Sinclair Spectrum or, an MSX, and in the Apple it delivers an impressive stereo sound thanks to both channels being present. Interestingly though, it delivers a far smoother output than an MSX playing the same music, probably because of a superior filtering circuit.

She wraps up with a discussion of coding on the Apple for the AY, and how to best accommodate the card on the later Apple IIgs. If the AY chip catches your interest, it’s also easy to drive from a microcontroller.

21 thoughts on “A Deep Dive Into The Sound Of An Apple II

  1. while a nice article, I wouldn’t necessarily call this a “deep dive” into Apple II sound (I say this as someone who has spent the last few years doing extensive Apple II sound programming for game demakes and demoscene coding).

    A deep dive would talk about “Electric Duet” which allowed multichannel sound using just the speaker, or the earlier ALF music cards, or the 12-channel Phaser cards. And also get into speech synthesis cards with S.A.M. or the now un-obtanium SSI-263P chips that can add speech to the Mockingboard cards.

    1. I can explain that for you. Because the Apple ][ uses a low part count on the disk controller, Woz needed to make sure that the head was properly positioned for track zero. The easiest way to do this was just to keep moving the motor past where it would logically stop. So that loud clunking sound you’re hearing is actually the stepper motor hitting repeatedly after seeking to the beginning. Doesn’t do any damage but it is noisy.

      1. The Commodore 1541 did the same, especially after read errors or before a formatting operation. But it is only half correct, that it does no damage. It can (could) lead to head misalignment.

        1. That’s right and it was fixed with the 1541C by adding a light barrier (which was never properly marked as C model, btw; users had to know the art style of the drive’s front label). Unfortunately, Commodore used a pin of another chip for sensing, that was misused by the community for floppy speeders already. (These speeders were required, because the IEC serial interface of C64/1541 drives was utterly slow and broken twice. One crippling was related to VC20 backwards compatibility, I vaguely remember.) Hence, that very useful fix was removed in the 1541-II again, in order ro restore compatibility. What a mess. Best to stay away from the 1541 series and get a 1570/1571 perhaps.

      2. Ha, brings back memories of working at what was the first computer camp in the country in 1982 – lots of TRS-80 models 1’s and Apple 2’s. There was a “banned” program for the Apple that I had to repeatedly remove from campers computers that used the sound of the disk drive to provide the sound effects for sexual on-screen animations . I think this may have been my first exposure to computer porn. It mostly made me shake my head and tell the campers to get outside in the sunlight a little more…

    2. Another fun fact about the disk sounds is that depending on the OS / loader routine the seek sounds will be extremely different. This has a lot to do with the variations used for sector ordering and track layout. The crazier copy protection schemes used a spiral sector layout which was very difficult to copy for a very long time and man they sound so different than, say, Dos 3.3.

      1. The spiral track was very clever but because the “disk controller” in the Apple 2 was very temperature unstable, it often had problems reading disks, that could be resolved by hitting the controller card with a heat gun or a freeze blast right before trying to read the disk.

  2. Back in the day I PEEKed and POKEed in Apple BASIC to click the speaker. That typically didn’t work well so I learned enough 6502 assembler to buzz out a couple simple melodies. I got pretty much nowhere but I haven’t had that much fun since.

  3. My Apple II has quite the synthesizer built in. 15 voices, from an Ensoniq IC. But it’s a IIGS.

    I had an AY-3-8910, I asked for a cosmetic defect in 1979, and they sent one. Played with it on my KIM-1, which of course had a suitable I/O port built in. As I recall, it could connect directly to a bus, but it was an idd device so for most CPUs, easier to go through something like the 6522.

      1. I didn’t have fancy stationary for an imaginary company, so I just asked for a cosmetic defect, thinking that might get me a freebie. I don’t remember if there was a cosmetic defect. I suspect they.might have sent it anyway, but at the time I figured they’d want a whole story.

  4. I just wanted to take this opportunity to mock the Apple II’s overall capability in comparison to the Ataris. No hardware sprites, no fine scrolling, no sound. And super-high prices. Yep: Sounds like Apple.

    1. Yes but the design of the computer is from 1977. The Atari product more comparable from that year had 128 bytes of ram and no framebuffer! We could argue over specs and which is a superior machine but I don’t think that’s relevant anymore. As for other Apple products I only like this one because Jobs had nothing to do with it. It would be a crazy world if Tramiel would have kept his company profitable and taken on the PC market successfully. But all of it is lost to history now, we do better to celebrate these crazy contraptions for what they are, not what they aren’t. 😉

    2. So that’s why my father has had gotten a Sharp back then. :)
      All the other popular platforms were too underpowered and pricey.

      Either ways, I think we must thank the Apple II and The Woz for creating an “open” platform with off-the-shelf parts. This really caused a trend for cheap expansion boards with edge connectors.
      That way, IBM got inspired to invent the PC Bus for the IBM Model 5150 maybe, which in the end essentially gave birth to the 16-Bit ISA Bus we hackers love so much. ;)

    3. One way the Apple II was better than the rest in 1977 was the expansion bus. More compact than the S-100 bus, and you didn’t fill it up right away be ause so much was on the Apple II motherboard. You could do quite a bit out of the box.

      And soon there were endless boards to plug in, some from Apple, but also from others. A soundcard, a better videoboard, top off the memory, add a Z80, 6809 or eventually a 68000. There were popular boards, and niche boards.

      The other all in one computers had expansion, but for one perioheral, unless you added an expansion section.

      1. There was an arcade board for the Apple ][ which basically provided sprites and such. It offered the same TMS 9918A chip that was used in many platforms (MSX 1, Coleco, etc) but it was such a niche and never took off. By then developers for the platform learned to code without sprites using clever tricks like lookup tables, self-modifying code, etc. Sure it was a challenge, but you had games like Prince of Persia and Choplifter which started on the Apple // series. Since the CPU and Video scanner were interleaved, the Apple // had the advantage of not having to blank the screen when drawing video. On the other hand it lacked useful interrupts for getting precise timing for raster effects (but there were ways to pull it off and some really badass devs did so.)

        Mockingboard was definitely a popular add-on for gamers. Even though only a few dozen games supported the card, it really made for a better experience! But yeah, I’m just happy to have a MiSTer so I can enjoy all the 8-bit platforms that I missed out on back in the day. It would have been so different growing up if MSX had taken off in the US.

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