This comes a little late, but seeing how Zvon just released their latest expansion pack for Caustic, I thought I should give them a mention.
One of the biggest complaints I got from new users in Caustic v1 was the limited demo content. This was done for a few reasons:
1 - I wanted to keep the APK size as small as possible. The bigger the APK, the less likely people are to update or even download to try.
2 - Copyright issues. It's really hard to find free content on the 'net that you're allowed to re-distribute. Plenty of free stuff out there, you just can't include it, especially if you're charging for your product.
3 - I wanted to encourage people to use their own samples and find their style. Sample-based machines in Caustic have always accepted WAV files as a starting point.
I realized after seeing user videos and hearing songs sent in that people tend to use what came with the app. I guess as a mobile app, you're not always connected to your library of content or have the ease of browsing large sample websites for new stuff. So for Caustic 2, I wanted to add a direct way of finding new content. If you haven't seen it already, there's a "Get More" button in the preset selection popups for each instrument that launches a Market search for content packs. As a start, I created a pack from all the content sent in over the app's first 6 months of existence, donated by Caustic users. I will continue to make free expansion packs whenever I get enough content sent it to do so.
Zvon have been around the music content game for quite a while, and they offer really unique samples you won't find anywhere else. Perfect for getting those creative juices flowing and trying something new. There already have 10 packs available for Caustic: some free, some paid, but the paid ones are only a buck or two. The latest is a prepared electric piano where they heavily modified a Rhodes to get all kinds of sounds out of it.
Les Productions Zvon's packs on Google Play
They also offer a non-APK (just a zip file you install manually) set of single-cycle waveforms for use in the PCMSynth on their website. Transforms the PCMSynth into a bit of an analog synth... There's also info about their other products so feel free to write them if there's something they make you'd like to see brought over to Caustic.
Les Productions Zvon's website
For PlayBook customers, Zvon have made a dedicated site where you can get their kits for use with the PlayBook version.