The WavFile class http://www.labbookpages.co.uk/audio/javaWavFiles.html claims to read and write wav files and allow per-sample manipulation through arrays of sample values. It's certainly reasonably small, 23kbytes total source code.
I did struggle for a while to build an android app with the Wavfile Class included. This turned out to be because both WavFile and ReadExample (from the above link) were intended as standalone java programs, so include a method main(String [] args){}
. Eclipse sees this and thinks the Class is a standalone runnable program, and, when I click the run
button, tries to execute just the one Class with the java in the development machine, instead of launching the whole app to my phone. When I take care to run the whole app with the little drop-down menu on the run
button, I don't have any trouble, and the WavFile Class and examples drop straight in, give zero warnings in the IDE, and work as advertised running on my phone.