Question

I’m playing with the Alsa API and I wonder which parameters I should pass to the function snd_pcm_writei to simply play the solfège syllables/notes (A-G / do re mi fa sol la si do).

Thanks

Answer 1

If you really want to do it with that function, generate a waveform in a buffer. A triangle-shaped wave may not sound too awful and should be simple enough to generate.

The base “la” (A) is 440Hz, that is, 440 cycles of the waveform of your choice per second.
The other notes can be obtained by multiplying/dividing by 2^(1/12) (1.05946309) for each half tone above/below this base frequency. You will need to know at what frequency the output device is set up (that’s probably an argument to another ALSA function). If the device frequency is, say, 44100 Hz, and you want to play the base “la”, each period of your waveform should occupy 44100 / 440 or about 100 samples. Pay attention to the sample width and the number of channels the device is configured for, too.

Explanation: there are 12 half tones in an octave, and an octave is exactly half (lower pitched) or double (higher pitched) the frequency. Once you have multiplied 12 times by 2^(1/12), you have multiplied by 2, so each half-tone is at a factor of 2^(1/12) above the previous one.