For this example to work properly, you must first download Example 51 and save it with the name “xfade~.maxpat”. Then you must ensure that your xfade~.maxpat file is in the Max search path, or you must save this example patch in the same folder as the xfade~.maxpat file and reopen it, so that this patch can find the xfade~ object.

This example demonstrates two ways to establish the initial crossfade value of the xfade~ abstraction. The example on the left uses an initial float argument to establish the initial crossfade value. If you double-click on the xfade~ object on the left, you will see that the two objects that had a #1 argument in the subpatch now have the number 0.1 in those places. This sets up the object so that the cycle~ 440 will have an amplitude of 0.9 in the mix, and the cycle~ 465 object will have an amplitude of 0.1 (about 19 dB lower). The example on the right uses a control signal from the line~ object to provide the crossfade value. So in this case there’s no point in typing in an argument in the xfade~ object, because it would not be used by the MSP objects in the subpatch anyway. The argument to the line~ object, however, is important, since it establishes the initial value of that signal. That’s where the real initialization takes place for the crossfade value of that xfade~ object.

Notice that the number boxes in these examples show a value of 0 initially, which does not accurately represent the actual initial crossfade value. So if these objects will be presented to the user, and you want them to show the correct value, you would need to initialize them to the value 0.1, too. You could do that with a loadbang object triggering a message of 0.1 or set 0.1.

The gain~ sliders are provided so that you can choose to listen to one or the other of the two halves of this example.

This example uses the subpatch from the previous example, so it requires that you download the file mix~.maxpat and save the file, with that same name, somewhere in the Max file search path.

This example demonstrates the use of the line~ object to make a linear control signal, which is used to control the balance between two audio signals. (A “control signal” is a signal that’s not intended to be heard directly, but which will affect some aspect of another signal, or perhaps will control some global parameter of several sounds.) The line~object receives a destination value and a ramp time, and it then interpolates, sample-by-sample, from whatever its current value is, to ramp to the specified destination value in exactly the desired amount of time.

The mix~ object expects a control signal from 0 to 1 in its right inlet to specify the desired balance between the two audio signals in its left and middle inlets. When the control signal is 0, we hear only the first input sound; when the control signal is 1, we hear only the second input sound. Inside mix~, the two sounds are scaled appropriately according to the balance value in the right inlet, added together, and sent out the outlet. So to do a smooth linear crossfade between sound 1 and sound 2, it makes sense to send a linear control signal from 0 to 1 into the right inlet.

The two cycle~ objects provide constant full-amplitude tones (the pitches A and B), so they’re good sound sources to allow us to hear the effect of the crossfade clearly. The toggle is used to initiate a crossfade from one sound to the other; it provides a 1 or a 0 as the destination value for the balance. First we need to supply a ramp time, in milliseconds, in the right inlet of the pack object. When the destination value comes from the toggle, it gets packed together with the ramp time as a two-item list, and passed to the left inlet of line~. Over the course of that specified time, line~ calculates the intermediate value for each sample that’s needed in order to describe a straight linear progression toward the destination value.

The line~ object is thus a control signal generator, and importantly, it’s an object that provides an interface between the Max scheduler (the normal world of Max in which individual messages occur at a specific instant in time) and the MSP signal chain (in which a continuous stream of audio samples are being calculated). A single message to line~ triggers a change in its output signal, a change which could take place over any desired amount of time. You can also think of line~ as a “smoother”, allowing a signal parameter (such as amplitude, frequency, etc.) to change smoothly from one value to another.