The ability to use USB control surfaces for mixing is one feature that ACID Pro has which ACID Music does not. Control surfaces allow the user to assign fader buttons, knobs, and buttons on the controller to correspond with the mixing controls in the software. This allows hands-on real-time manipulation, which is a lot more convenient than using a mouse, one that many old school engineers are used to.
Audio on CDs are recorded at a bit depth of 16 bits (a measure of how many bits of audio is captured) and a sample rate (the number of times audio is measured per second) of 44.1 kHz, both which define overall audio resolution. ACID Music has a maximum 16 bit/48kHz audio resolution, while ACID Pro has 24/192kHz. This makes for a slightly more detailed-sounding audio. The trade off is that the higher resolution files take up more hard drive space, up to three times, more depending on the specific settings.
The input bus tracks is a feature exclusive to ACID Pro. This means that effects sent via the "insert" or "send" inputs can be applied to the input signal, as well as give the ability to configure which hardware inputs are specifically used. Another exclusive ACID Pro feature is the ability to render projects in real time. This means external sound sources can be mixed down as part of the ACID project.
Included with ACID Music, not the Pro version, are two VST plugins. One is the Studio Devil British Valve Custom (BVC) guitar amp, and emulation based on the Marshall stack. The other is TruePianos Amber Lite, a cut-down version of the software instrument of the same name which has controls for dynamics and reverb.