Arithmetic and the teaching of arithmetic have been constantly evolving from ancient civilizations to the present day. Arithmetic began to evolve because people needed numbers. There have been various number systems in history, and some of them are still used today. The most widespread is the Arabic numeral system (which originated in India) and is taught in the initial teaching of mathematics today. Teaching the concept of number is a complex process that moves from concrete to abstract. In modern teaching, numbers are formed gradually using concrete materials and different models, such as Pamela Liebeck’s ELPS (experience, language, pictures, symbols) model. Modern initial teaching of arithmetic is based on principles, methods, forms of work and various teaching aids. All principles are equally important, so it is important to change and supplement them at the right time with different methods and forms of work. There are many visual teaching aids for introducing the concept of number, but there are not many auditory aids. Gardner's Theory of Multiple Intelligences shows the importance of interdisciplinarity in teaching. Mathematics and music are connected on several levels, so their connection in teaching contributes to the development of complete knowledge. Music in mathematics teaching can effectively increase students’ intrinsic motivation and positively affect their interest and concentration. The aim of this paper is to describe the historical development of arithmetic, to explain the complexity of the formation of the concept of number, and to describe the principles, methods, forms of work and teaching aids used in the introduction of the concept of number. In addition, this paper discusses the deep connection between mathematics and music and finally presents musicalized songs as a means of introducing the concept of numbers up to 20.