Finally written it up here: http://octoberclub.w...-making-sounds/

The fully working project is on github:

https://github.com/o...uino.PiezoTest2

and here's the modified code to calculate frequencies:

using System; using Microsoft.SPOT; public static class NoteFrequencies { /// <summary> /// Static method to calculate the frequency of a note from its name and octave. /// </summary> /// <param name="octave">Octave number (0-7)</param> /// <param name="note">Note to be found: eg. F#, A, Bb</param> /// <returns></returns> public static float CalculateFrequency(int octave, string note) { string noteLC = note.ToLower(); string[] notes = "c,c#,d,d#,e,f,f#,g,g#,a,a#,b".Split(','); // loop through each note until we find the index of the one we want for (int n = 0; n < notes.Length; n++) { if (notes[n] == noteLC // frequency found for major and sharp notes || (note.Length > 1 && noteLC[1] == 'b' && notes[n + 1][0] == noteLC[0])) // or flat of next note { // Multiply initial note by 2 to the power (n / 12) to get correct frequency, // (where n is the number of notes above the first note). // Then mutiply that value by 2 to go up each octave return (16.35f * (float)System.Math.Pow(2, (n / 12))) * (float)System.Math.Pow(2, octave); } } throw new ArgumentException("No frequency found for note : " + note, note); } }