[LAU] Calculating the sine wave frequencies from the midi key

Hi there, There's a line in the midisine.c code at jack's example client directory. In this code, Ian Esten has calculated note frequencies in the function below: void calc_note_frqs(jack_default_audio_sample_t srate) { int i; for(i=0; i<128; i++) { note_frqs[i] = (2.0 * 440.0 / 32.0) * pow(2, (((jack_default_audio_sample_t)i - 9.0) / 12.0)) / srate; } } after that, a variable called ramp is used to form the sine wave samples in the function process: ramp += note_frqs[note]; ramp = (ramp > 1.0) ? ramp - 2.0 : ramp; out[i] = note_on*sin(2*M_PI*ramp); I actually understood what the code does. But can someone show me a place to read information about the equation: note_frqs[i] = (2.0 * 440.0 / 32.0) * pow(2, (((jack_default_audio_sample_t)i - 9.0) / 12.0)) / srate; I couldn't catch the relationship in the calculation above. Thanks. -- Arda EDEN Cumhuriyet University Faculty of Fine Arts Department of Music Technology Sivas/TURKEY