There are times when you may want to join some audio files to make one audio file which should be the combination of different audio files which you want to combine. There are many softwares which we already covered for this purpose, you can refer some old articles at the links below.
Combine, Mix Two Or More Audio Files Of Different or Same Format, read here
Combine, Join Multiple MP3 Files Into One MP3 File, read here
Create, Combine Two Different Format Audio Files Into One Using Helium Audio Joiner, read here
But there are times when you need to cut songs, overlap and cut a part of songs and merge them together to get one single song, for that purpose the above mentioned softwares may not work well as per your requirement. For this purpose you can use the free tool called Audacity as shown in the image below.
You can keep adding multiple number of unlimited songs and merge different parts of them viewing them in timeline mode as shown in the image below.