Here are some of my experiences playing with LPC programs. I'll list the paid ones first and then the free ones.

The most widely known, perhaps, is a vst called Bitspeak. It can use a sampling rate of 8000 to 44100 HZ, so you get to hear how LPC would sound in a wideband context if you choose. It's cool, but has some weird inaccuracies. The voiced sounds always seem too loud to me, and the noise and tonal circuits seem to be separate so both can be produced at once. I could be wrong, but I think? in real LPC encoders, at least older ones, only one can be produced at a time. I believe many encoders have a pitch quantization that takes effect at high notes especially. The higher the pitch, the more gritty the pitch becomes, until it starts to sound like some aggressive nightmarish form of autotune. I once heard a cat on an 80s toy whose pitch was so quantized that it was almost meowing a chromatic scale. In Bitspeak this does not happen, though some people may consider this a benefit.

Plogue makes a plug-in called Chip Crusher. It emulates the sound of avrious old sound chips and even lets you put that sound in a simulated room and speaker setup. It has an LPC mode which works pretty well but is limited because of the 8000HZ sampling rate, and apart from adjusting the misc settings, there's no way to adjust LPC parameters so far as I know. It's been a while since I tried it.

Izotope has a plug-in called Vocal Synth which has an LPC mode called Compuvox. It's been a while since I played with it, but it seemed to work pretty well.

Now for free stuff. There's a really old command line program called rtlpc. I still have it lying around but it's ancient. The last time I tried it was on XP, and the last time I ran it, it blue-screened, though that computer was living on borrowed time. It allowed you to listen to your microphone encoded to LPC in realtime, and you could adjust a lot of parameters with keystrokes. It operated at a 22K sampling rate so far as I could tell, but its time resolution was a mess. Words sounded distant and garbled no matter what you did. But it was still fun to try messing with stuff and see what differences it made, if any.

You can also use a free plug-in called MDA Tracker, which will turn your signal into buzz and noise. You then vocode this buzz and noise signal with the original, using something like MDA Talkbox or another vocoder, to produce LPC-like results. I personally prefer MDA's Talkbox for this, but any will work, at least to some extent.

Finally, some speech codecs which either work directly using LPC or have LPC-like modes: The old Speex codec will revert to some LPC compression if you set the quality very low, though it sounds raspy and muffled. Another encoder, again unsupported but a lot older is called Toolvox gold encoder. It takes a lot of digging to find, but it is meant to be a demo of a low bitrate speech codec that encodes at iirc 2.4kbps. While it doesn't sound exactly like LPC, it's very close and sounds pretty good for what it is. And of course the free LPC10 codec is included in Sox. There are many other speech codecs which work using LPC as well, but they are mostly proprietary.

If I find anything else, I will be sure to add it to this list. I'd be grateful for input and other suggestions also.

fun fact: agomez92 used bitspeak for the menu voices (accept the main menu voices, as they were recorded from a braille n speak) in order to emulate ti's implementation of lpc, as it was used in many arcade games (mostly from atari).

Sorry I forgot that, I was in a bit of a rush since I had to bring my computer back to the cottage where the internet sucks.