The Russian Morse code approximates the Morse code for the Latin alphabet. To memorize the codes, mnemonics are used, called "melodies" (напевы).
A "melody" for a morse code for a character is a phrase which is sung (hence the name): the syllables with vowels а, о, ы correspond to dashes and sung long, the other syllables and the syllable "ай" correspond to dots and sung short. The "melodies" differ among various schools.