update readme about instrument.h

README.md

@@ -2,4 +2,20 @@
 
 This is mostly just a little wrapper around paul's teensy audio library synth_wavetable, updated to make sure it runs on the ATSAMD51 with adafruit's atsamd fork of Audio.
 
-the `decoder.py` here is taken the teensy AudioSynthWaveform repo, with changes to make it output parsed soundfonts in the format expressed in the `synth_wavetable.cpp` file from the Audio repo
+the `decoder.py` here is taken the teensy AudioSynthWaveform repo, with changes to make it output parsed soundfonts in the format expressed in the `synth_wavetable.cpp` file from the Audio repo
+
+if you run decoder on a soundfont, it'll drop the headers in src/instruments. then you can edit `instrument.h` and change these lines:
+
+```c++
+#include "instruments/AnalogSaw_samples.h"
+auto instrument = AnalogSaw;
+```
+
+to, for instance,
+
+```c++
+#include "instruments/lead_samples.h"
+auto instrument = lead;
+```
+
+and that'll be your instrument now.