Hardware
- Acoustic pickup for reading string vibration via audio input: https://www.google.com/search?aq=f&ix=iea&sourceid=chrome&ie=UTF-8&q=acoustic+pickup
- Audio input to Android phone via headphone port:
- https://www.youtube.com/watch?v=sz-9mxWa2VA
Android
More portable but maybe harder, should start with laptop approach (below)
Spectrum ("EQ") Android apps
- $2: https://market.android.com/details?id=com.julian.apps.SPLMeter&hl=en
- Free: http://www.androidzoom.com/android_applications/music_and_audio/spectral-audio-analyzer_bbhl.html
Android graphing/audio libraries and code
- Charting: http://code.google.com/p/chartdroid/
- Audio input processing: http://stackoverflow.com/questions/7686898/reading-data-from-a-microphone-in-android-to-process-it-online
Laptop approach
- Android lacks low-latency audio interfaces, so maybe better to just use a laptop
- guitar pickup direct to microphone input
- use a simple Processing app
Related projects/work
- Eddy Flux (via Mathew) -http://atmos.seas.harvard.edu/lab/brazil/lbaflux.html
- Page 4 (via Adam) - http://nadp.sws.uiuc.edu/lib/brochures/nitrogen.pdf