I am brand new to PD. I have been messing around a bit and watching some tutorials. I was watching a tutorial where midi notes that were output from PD were played in FM8. Depending on the channel, a different instrument was used in FM8. I was wondering how something like this works on android. I found a tutorial for building a guitar tuner that received input from the microphone, but not much about how sound is played. All I could find were some discussions about how real time MIDI is not support. Presumably this means that you need to output to a file and then ask the media player to play it back? Is there any way to select different instruments? Or is there some altogether different approach like including patches that produce guitar sounds. I guess my general question is whether or not you can build a stand-alone application that simulates multiple instruments without having to involve other 3rd party applications to actually play the sound?

LibPD is available for the Android platform, it's meant to be the vanilla PD, without a UI: you need to write code.

To play sound on and Android device you would include patches, and possibly sound samples, that the patches use. Just like using PD on a laptop/desktop computer.

Bear in mind that Android devices do not have immense processing power, so trying to reproduce a whole orchestra might sound a bit crackly.