JUNE 24, 2021

Exploring Increased Voices, Tracks, and I/O in Pro Tools 2021.6

Pro Tools UI showing voices system usage

Pro Tools 2021.6 raises the voice, track, and I/O counts for both Pro Tools and Pro Tools | Ultimate. The increased voice and track counts enable you to create even bigger sessions, and more I/O means that you can record more sources and connect more outboard gear when you’re using a Core Audio or ASIO interface. But what are voices, why do they matter, and why are there limits at all?

To answer these questions, let’s go back to basics.

Voices and Streaming

When Pro Tools plays back audio, it uses voices to stream the audio from your hard disk to the Pro Tools audio engine. One audio stream uses one voice, so a mono stream uses a single voice, but a stereo stream uses two voices, and a 5.1 stream uses six voices. In Pro Tools, audio from disk (and to disk for that matter) is handled by Audio Tracks. Therefore, Audio Tracks use voices. Again, a mono Audio Track uses one voice, a stereo Audio Track uses two voices, and so on.

In normal circumstances, it’s only Audio Tracks that use up voices. Pro Tools has many different track types: Aux Inputs, Instrument Tracks, VCA Masters, Video Tracks, etc., that do not use up voices. So, when we talk about track limits in this article, bear in mind that we are talking about Audio Tracks only. You can create thousands more tracks in total in your Pro Tools session, and you can find the details here.

In fact, you’ll be hard pushed to hit the track limits in Pro Tools, no matter how big your sessions are!

Voices and tracks in Pro Tools | Ultimate

So now that you understand the link between voices and Audio Tracks, we need to look at how we count them in Pro Tools and Pro Tools | Ultimate.

When we state the limit in Pro Tools | Ultimate we refer to a voice limit. Prior to Pro Tools 2021.6 the limit was either 256 voices per card for HDX systems (a maximum of 768 for a three-card system) or 384 voices when using a Native audio engine—HD native, Core Audio, or ASIO. How those voices are used depends on the session. You could use 256 voices by creating 256 mono tracks or use up the same number of voices by creating 32 7.1 tracks. Another point to bear in mind is these voice counts are halved when you double the sample rate.

So how does Pro Tools 2021.6 change this? The first thing is to say that if you are using HDX Classic—i.e., the Hybrid Engine is turned off—then the voice limitations are the same: 256 voices per card, because the voicing is handled by the hardware. However, if you are using the new HDX Hybrid Engine or any other native playback engine—HD Native, Core Audio, or ASIO—then the voice count goes up to a massive 2048 voices, more than twice the number that you would have with a three-card HDX system! Not only that, you get 2048 voices at all sample rates. This gives you the potential to build huge Pro Tools sessions.

new tracks window in Pro Tools

voices count in Pro Tools

The Pro Tools | Ultimate Audio Track limit is also raised to 2048. Pro Tools | Ultimate allows you to create more tracks than can be voiced. For example, you could create 256 7.1 Audio Tracks, which will use up your 2048 voices but not your Audio Track count. However, it’s possible to switch a track’s voicing from Dyn to Off in order free up voices, giving you lots of flexibility.

switch off track voicing in Pro Tools

Voices and Tracks in Pro Tools

So what about Pro Tools? When we state the limit in Pro Tools we talk about maximum number of Audio Tracks, not voices. Prior to Pro Tools 2021.6, the maximum number of Audio Tracks that you could create with Pro Tools was 128. And, like Pro Tools | Ultimate, the Audio Track count would halve when you double the sample rate.

If you’re following closely, you will realize that if you create 128 mono Audio Tracks in Pro Tools then you will be using 128 voices, and if you create 128 stereo Audio Tracks in Pro Tools, you will be using 256 voices. This is just a by-product of counting tracks rather than voices and, in the end, it’s easier to keep tabs on the track count than voice count.

How do things change with the release of Pro Tools 2021.6? The good news here is that the Audio Track count doubles from 128 to 256 Audio Tracks. The even better news is that doubling the sample rate no longer halves the available Audio Tracks. If you are someone who likes to work at 96kHz then you will now have four times as many Audio Tracks at your disposal than you had previously!


new tracks window in Pro Tools with 256 tracks

In summary, Pro Tools 2021.6 opens up a whole world of possibilities when it comes to creating larger, more complex sessions.

Ins and Outs

As well as the increase in Audio Tracks and voices, we have also addressed a long-standing request in Pro Tools 2021.6: I/O. For many years, Pro Tools users with a Core Audio or ASIO interface have been restricted to a maximum of 32 inputs and 32 outputs on their interface. Users who require more I/O, usually for the purposes of recording large numbers of instruments, needed to buy HDX Systems. This makes sense if you’re recording many simultaneous performers, say in a scoring session, as you will benefit from the guaranteed performance levels that HDX provides.

Pro Tools 2021.6 increases the maximum I/O to 64 inputs and outputs when you are using non-Avid hardware. This is a benefit to a several types of users. You may want to record a feed from a live sound mixing console. Invariably, there will be more than 32 channels to record, and having to take an HDX System on the road is not an ideal solution as you will want something that’s compact and rugged. Increasing the input count to 64 enables more live sound workflows.

The other type of user who will really benefit from the I/O increase is somebody who has a lot of outboard hardware and needs to incorporate it into their Pro Tools session using hardware inserts. Increasing the I/O count to 64 enables them to leave their hardware permanently patched into their Core Audio/ASIO interface and not have to keep re-patching.

Why Have Limits?

One final point that I want to address is why we have these limits at all—why not just remove all limitations? Pro Tools has always been a rock-solid audio production platform. One of the reasons for its longevity and prominence in the industry is the fact that it can be trusted. To provide this stability, every aspect of Pro Tools is thoroughly tested. Therefore, when we put a limit on anything in the software, you can be sure that we’ve tested it to that limit to give you, the user, confidence in your Pro Tools system.


I hope that you’ve found this article useful and you’re making plans as to how you can make use of even more audio tracks in your next project! For more information on other new features in Pro Tools, check out our What’s New article.

  • Dave Tyler headshot

    I've worked in the audio industry for over 25 years and I'm still passionate about the technology that enables talented, creative people to produce amazing music, films, and TV shows.

  • © 2024