Slate Digital Virtu

Struggle with DIY mastering but can’t afford a pro? Perhaps Virtu can help you apply some polish...

Virtu is a machine‑learning‑based online mastering service: you upload your tracks (stereo WAV files, ideally at 44.1 or 48 kHz, and no bigger than 200MB), then choose from a few options and, after deliberating for a few seconds, Virtu will select 15 seconds of your uploaded track and create a preview of a mastered mix. If you like what you hear, you pay, and can upload the mastered mix to your streaming platform of choice. If not, you can try with different settings.

Originally offered only as part of Slate Digital’s All Access Pass bundle, Virtu is now available to non‑subscribers, who get two free credits on registering payment details (though note that the non‑subscription version costs a little more per track).

Overview

Virtu defaults to a Universal mastering style, but you can switch to a genre‑specific option (Pop, Rock, Hip‑Hop, EDM or Instrumental), each guided by a different production aesthetic. For example, the Instrumental settings tend to work well when there are lots of mid‑frequency sounds, while Hip‑Hop will prioritise firming up the bass. As with the Waves equivalent I reviewed in March, there’s also a reference track feature: upload the track you’d like to reference (WAV only) and Virtu will match its EQ curve and loudness profile. You have three loudness choices: Streaming Standard (‑14 LUFS), All Round (‑11 LUFS) or CD Level (‑8 LUFS). If you change settings, Virtu takes just a few seconds to compute the difference. Helpfully, if your browser settings don’t allow Virtu to play back audio, a prompt appears to tell you which settings you need to change — this happened to me when using Safari on a Mac.

Advanced mode doesn’t take you down any complicated rabbit holes...

The mastering process treats each track individually, taking into account its peak, RMS, and average levels in multiple frequency bands. That information informs the EQ curves, multiband compression and limiter settings and so on. At this stage you can press the Master button and let Virtu do its thing, but there are also some Advanced controls you can try before doing so. Advanced mode doesn’t take you down any complicated rabbit holes — it simply opens up three sections, each with a few further options. In the Frequency Balance section you can opt for Default, Deep or Gentle for the lows, and Default, Bright or Smooth for the highs. In the Compression section you can switch between Unchanged and Compressed, with Balanced, Punchy or Aggressive choices for the compression. Finally, the stereo can be Unchanged, Balanced or Wider. These are all on/off selections.

In Advanced mode you can tweak the default processing of the genre‑based presets, selected in the main screen.

You can hear the effect of all these changes on your preview, which appears at the top of the screen as a waveform envelope with a play button. As on the main screen, when you make changes the preview has to be recalculated, but that takes only a few seconds.

Once you commit to mastering a track, you use up one of your credits. All Access Pass subscribers get three free credits per month; additional credits then cost very little. If you decide a finished track isn’t quite right, you can change the settings to remaster it, but it will cost you a credit. Those who don’t subscribe get two free credits when they first use Virtu, but after that you buy credits — though it costs slightly more, it’s not expensive, and could still be a good option for occasional users.

Tracks appear on a playlist‑type screen along with icons showing which presets were used, the date, download buttons and so on. You can also compare mastered tracks with their unmastered version. As the mastering takes place on a remote server, mastered tracks must be downloaded once you’re happy with them; they’re stored on the server for 30 days before being deleted.

Virtu Reality

Providing you feed it a decent mix in the first place, the results are generally impressive, and while a skilled mastering engineer would certainly be able to apply more finesse (especially where different sections of a song need to be treated very differently), the genre types on offer here allow the user to choose a preset that will work well for most musical styles. The processing doesn’t feel too heavy handed, yet it does ‘that thing’ where detail is lifted out, bass is firmed up and the mix made to sound generally more cohesive. It also controls the loudness to optimise it for the various release platforms.

Used on my own material, the end results weren’t far away from what I achieved using Logic Pro’s own built-in mastering tool, which has the slight operational advantage that there’s a slider that allows you to apply more or less of what the algorithms thinks is ideal. But if anything the Virtu mixes sounded slightly more weighty, and Virtu provides you with more genre options too.

As with most mastering programs, Virtu seems to gravitate towards applying a gentle smile curve to lift out both lows and highs, but if you think it has gone too far you can use the master EQ options to dial that back. After all, Virtu is touted as being a mastering assistant, not a mastering engineer, so you still have to use your ears to decide whether the end result is what you wanted to achieve. As long as you optimise the settings in the preview, so that you don’t need to revisit tracks, the process is very cost effective. And while home recordists creating their own streaming material might be seen as the primary market, I’d say that Virtu also has a role to play in the pro studio — it could be a great way to send clients home with preliminary mixes that give them a good idea of how the finished track might sound once professionally mastered.