See the sticky How to install a contributed library (I wonder why stickies in this forum don't remain on top?).
Anyway, the idea is that you put the library in the sketches folder, not in Processing's install folder!

I tried what is in the sticky but I still get the same error. Any help?

I'm running Sonia for the first time and I'm having quite the same problems.

The folder "sonia_v2_9" (uncompressed, of course) is in Documents > Processing > libraries as instructions say. It contains the four files it uses to come with. Other libraries in the same folder work ok. Processing imports Sonia from the menu but I got always the same message for all examples I'm trying to run:

NullPointerException

Could not load native library for JSyn V142
com.softsynth.jsyn.SynthException: JSyn error: Could not access JSyn synthesis engine.  -  JSyn not properly installed, or web page is not calling smart_embed_jsyn.js!, 0x0=0, 0x0=0
Sonia: Please make sure you have entered the correct Sample file name to load
Exception in thread "Animation Thread" java.lang.NullPointerException
    at pitaru.sonia_v2_9.BJSyn.loadSample(BJSyn.java:269)
    at pitaru.sonia_v2_9.Sample.<init>(Sample.java:38)
    at sample.setup(sample.java:33)
    at processing.core.PApplet.handleDraw(PApplet.java:1383)
    at processing.core.PApplet.run(PApplet.java:1311)
    at java.lang.Thread.run(Thread.java:613)

In the code, the line   mySample = new Sample("sine.aiff");   is highlightened.
But the sample sound file in project/data folder has the same name than in the sketch.

(I'm working with MacBook Pro, OSX 10.4.11)

Can't figure out what I'm doing wrong. Thanks for any help.

Sorry. I've found the problem. Plugin installation was not successful at first time, and I thought it was ok.
( http://www.softsynth.com/jsyn/plugins/install_plugin.php)

Hi,

I've had the same problems, then I downloaded the JSyn plug-in, and dragged jsyn-beta-16.5.14 into my sketch too. The error shown above has stopped, however my line of code:
  LiveOutput.start(bufSize, bufSize*2);
is still being high-lighted, and the following is showing in the console:

JSyn: default output latency set to 80 msec for Windows 7
Audio: AudioDevice: Primary Sound Driver, max in = 0, max out = 2
Audio: AudioDevice: Speakers (High Definition Audio Device), max in = 0, max out = 2
Audio: AudioDevice: Primary Sound Capture Driver, max in = 2, max out = 0
Audio: AudioDevice: Microphone (High Definition Aud, max in = 2, max out = 0
Audio: AudioDevice: Port Speakers (High Definition Audio, max in = 0, max out = 0
Audio: AudioDevice: Port Microphone (High Definition Aud, max in = 0, max out = 0
  java.version = 1.6.0_37, java.vendor = Sun Microsystems Inc., os.arch = amd64
---- Pure Java JSyn www.softsynth.com - rate = 44100, RT, V16.5.14 (build 448, 2012-12-10)
Input Device #2: Primary Sound Capture Driver has 2 channels
Input Device #0: Primary Sound Driver has 2 channels
Output buffer size = 14112 bytes.
Output Latency =  80.0 mse

These are just specs though, not helping me troubleshoot why my code won't run :s
Any tips please?