We've gone to great extents to make SALSA look as good as possible with as few blendshapes as possible. However, for those of you that would like to try SALSA with fewer blendshapes, this is possible as well, and the results are pretty good. For the purposes of this article, we'll be using SALSA 3D, but the principles work with SALSA 2D as well.
SALSA uses four (4) mouth positions in normal operation. This requires the configuration of 4 basic mouth shapes on your model. However, you can implement SALSA with 1 - 4 shapes; although, using one blendshape will generally net out little to no motion. To use the minimum mouth shapes, configure your sayRest position in the sayRest slot and then configure your second mouthshape index in the remaining slots as shown.
If you want to use 3 mouth shapes, you have a couple of ways you can configure them in the SALSA Custom Inspector as shown in the image below, with your second blendshape index in slot 2 (saySmall) and your third blendshape index in slots 3 and 4 (sayMedium & sayBig):
Or as follows, with your second blendshape in slots 2 and 3 (saySmall & sayMedium) and your third blendshape in slot 4 (sayBig):
The choice is yours and the effects are slightly different. Option 1 blends your 3rd blendshape in more frequently and at lower cutoff. Option 2 blends your 3rd blendshape in at the highest cutoff, less frequently overall than in Option 1. Of course, this depends on your audio file and can be further fine-tuned using the Custom Inspector properties.