Pure Data (aka PD) is a free alternative to Max developed by one of the originators of Max, Miller Puckette, and his collaborators.  Like Max, it is a graphical programming environment that links digital audio and MIDI.

The Max program to add sine waves is implemented in PD in Figure 2.29.  You can see that the interface is very similar to Max’s, although PD has fewer GUI components and no presentation mode.

Figure 2.29 Adding sound waves in Pure Data

Figure 2.29 Adding sound waves in Pure Data