I’m not aware of any other DAW which has a voice based system like Pro Tools does. I would imagine its a result of the DSP heritage of Pro Tools that all versions of Pro Tools have a system of voices which is distinct from the maximum number of inputs and tracks available. This is a similar situation to that found in polyphonic synthesizers where my synth might have 61 notes on the keyboard but I can only play 6 notes at any one time. In the same way Pro Tools can have far more tracks in session than can be played back simultaneously but as long as they aren’t all playing at the same time there is no problem.
How Many Voices Does My System Have?
For Pro Tools and Pro Tools Ultimate the maximum voices available decreases with increased sample rate. The following examples are all for 64bit Pro Tools systems (i.e. Pro Tools 11 and later).
If you have Pro Tools Ultimate you have 256 simultaneous voices available per card at 48KHz. Running HD software only without HDX hardware counts as running one HDX card.
If you have Pro Tools software you get 96 voices at 48KHz, considerably more than the 32 maximum simultaneous inputs available to non-HD hardware users.
If you are running Pro Tools First you get 16 voices regardless of sample rate.
How Do I Manage Voices?
The simplest way to manage your voice allocation is to understand how Pro Tools manages them. When set to “dyn” (dynamically allocated voicing) Pro Tools assigns voices from left to right across the mix window (or top to bottom down the edit window). If the total number of simultaneous tracks playing back exceeds the maximum it is the first track beyond the voice limit counted from the left which will be the first track not to play back. The simplest way to give priority to an important track is to move it to the left.
Of course there are many ways to mitigate voice stealing when sessions get large. The most straightforward is to bounce a stem of submixed tracks and to “hide and make inactive” the source tracks to free up some resources. On TDM systems it was possible to allocate fixed voices to specific tracks but In situations where I have run out of voices I have usually bounced a submix to eliminate the problem rather than try to stretch too few voices further than they want to go.
Native Plug-Ins In DSP Environments
DSP Pro Tools systems are designed to use DSP plug-ins whether they are HDX or TDM. As a result we encounter a couple of idiosyncracies. While DSP systems can use native plug-ins, native plug-ins exist outside the DSP environment and crossing this imaginary divide between the native and DSP worlds uses voices. Inserting a native plug-in under most conditions will use two voices, one for input and one for output and will add latency. The specifics of this are quite long-winded, see p953 of the Pro Tools Reference Manual for the details. A much more significant side-effect of this is that you can’t monitor through a native plug-in while recording on a DSP system. A simple workaround exists, simply insert a DSP plug-in before the native plug-in and all is well. The solution is far simpler than understanding why it is necessary in the first place but keep it in mind next time you’re trying to track electric guitars through a native amp sim on a DSP system.
Update - at NAMM 2019 Avid announced additional voices for Pro Tools in a future release.