I was not happy with the way the individual solo buttons were implemented during Beta Testing. Previously, you were able to use the Solo Icon to select tracks to be soloed and by selecting tracks, using the Cursor + Shift/Control buttons, increase or refine your selection of tracks. As the selected tracks were highlighted, the mix you had was easily identified even in the Classic Tracks Menu. The 2012 version of RB used individual solo button which had to be selected individually, but the Solo Icon could still be used to deselect all the soloed tracks at once.

Now with Build 4 the Solo Icon appears to be able to select a track as solo IF the track has been previously selected with the cursor, but cannot be un-soloed except by the individual track solo button. In fact, the original purpose of the Solo Icon has been virtually eliminated. This part of the program needs to be reviewed.