This is a very simple melody generator made in C.

melody-gen.c

// Copyright (c) 2021 Edwin Pratt
//
// This software is released under the MIT License.
// https://opensource.org/licenses/MIT



// Compile with
// gcc -Wall -Werror -Wextra -o melody-gen melody-gen.c

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

// Next note prediction.
// Should we step up or down, or leap up or down, or repeat the note?
// When leaping, we'll use a different variable called "leap_size" that ranges from 2-3 whole tones.
int available_note_preds = 5;
typedef enum _next_note_pred_t {
  STEP_UP,
  STEP_DOWN,
  LEAP_UP,
  LEAP_DOWN,
  REPEAT
} next_note_pred_t;

// Print the note
void print_curr_note(int curr_note) {
  char notes[7] = {'A', 'B', 'C', 'D', 'E', 'F', 'G'};
  printf("%c ", notes[curr_note % 7]);
}

int main() {
  srand(time(0));
  
  int bar_count = 2;
  int num_notes_in_bar = 4;
  int num_whole_notes = 7;
  int leap_size = 0;
  int curr_note = -1;
  
  for (int i = 0; i < bar_count * num_notes_in_bar; ++i) {
    // Get a prediction
    next_note_pred_t note_pred = 0 + (rand() % available_note_preds);
    
    // If no note was chosen before, skip this step and generate a random note.
    if (curr_note != -1) {
      switch (note_pred) {
        case STEP_UP:
          // Step up
          curr_note += 1;
          break;
        case STEP_DOWN:
          // Step down
          curr_note -= 1;
          break;
        case LEAP_UP:
          // Leap up
          leap_size = 2 + (rand() % 2); // 2 + [0, 1, 2] = [2, 3, 4]
          curr_note += leap_size;
          break;
        case LEAP_DOWN:
          // Leap down
          leap_size = 2 + (rand() % 2); // 2 + [0, 1, 2] = [2, 3, 4]
          curr_note -= leap_size;
          break;
        case REPEAT:
          // Note stays the same
          curr_note = curr_note;
          break;
      }
    } else {
      curr_note = 0 + (rand() % num_whole_notes);
    }
    
    print_curr_note(curr_note);
  }
  
  return 0;
}