The best alternatives to Pegboard Synth are Melody Generator, Listen to Twitter, and Melodist. If these 3 options don't work for you, we've listed a few more alternatives below.
Use Melody Generator to make random MIDI melodies. The melodies are procedurally generated and are royalty free. You can export the MIDI or WAV file to use in your own music.
If Tinder and Splice had a baby. The current process for music makers to find melodies is time consuming and frustrating. We're changing that with an on-the-go, efficient app showcasing melodies in an intuitive interface