Wednesday, November 11, 2015

App Review: Cortosia "Good Sound Tuner" by Korg

The newest app by KORG, Cortosia, is designed to be more than just a tuner, and claims to analyze and rate sound quality in real time. Let's this if the app lives up to the expectations.


Note: all tests for this review were done with an alto saxophone.

What is it?

The heart of Cortosia is the interactive radar chart which is a visual representation of the five elements that determine what a "good sound" is. Cortosia analyzes and rates your performance in real time. The goal of Cortosia is to give feedback to musicians about their playing, to inform them about their performance level and identify attributes of their sound that could be improved.


Although this is the main feature of the app, and one that sets it apart from the multitude of apps catering to musicians, Cortosia packs an impressive amount of additional features such as a time domain graph, practice log, automatic recording, global ranking system and metronome. We will come back to take an in-depth look at each of these, later in the review.

The app supports several instruments, with more added regularly. Flute, clarinet, trumpet, violin, cello, soprano, alto, tenor and baritone saxophone are currently supported.

Cortosia is only available on iOS and unfortunately isn't a universal app. You can use it on an iPad, and it works great, but it will display as a blown up iPhone app.


How does it work?

Cortosia uses the ARTISTRY (Automatic Rating Technology for musical InSTRument plaYers) technology, developed by Korg in collaboration with the University of Pompeu Fabra in Barcelona, Spain, to measure and rate the sound quality of instrumental performance.

The five elements analyzed are as follows:

  • PITCH STABILITY: the stability of the pitch in the sustained part of the note. 
  • TIMBRE STABILITY: the timbre stability in the sustained part of the note. 
  • DYNAMIC STABILITY: the quality of the loudness in the sustained part of the note. 
  • ATTACK CLARITY: the quality of the attack according to the most common playing technique. 
  • TIMBRE RICHNESS: the quality of the timbre in the most common playing technique. 

Although most of these attributes are self-explanatory, one could wonder exactly what defines "Timbre Richness". This is especially important for saxophonists, as timbre varies drastically from one style to the other, from one's tonal approach to another's. Brian at Korg's was kind enough to explain how timbre is handled by ARTISTRY:

Timbre Richness (TR) has been defined as an attribute which indicates whether a player has acquired a common skill to make good timbre, and we don't mean the attribute indicates how good the timbre itself is. Initially we focused on classical music players and therefore such timbres would be regarded as better ones in the current system. However the attribute would get more universal with some improvements later. In addition, TR is a complex attribute built using a powerful machine learning algorithm. The attribute uses something related to spectral information, but much more complex than a simple spectral analysis .

What is good sound? How does Cortosia work? Watch what Xavier Serra, Professor at the university of Pompeu Fabra, Barcelona, and director of Music Technology Group, has to say about it:

What is interesting and very promising is that ARTISTRY has been designed to learn over time. Although it had to be created based on controlled performances and ratings, the technology was developed so it could learn and improve with the data it collects.


A Detailed Look at the Features

1. Radar Chart & Time Domain Graph

Cortosia's main section, the "Practice Room" is the hub to many of the features of the app. The default view of this section is the Radar Chart, the main feature of Cortosia. How accurate is this Radar Chart? Quite simply it works extremely well with a caveat regarding timbre richness. As ARTISTRY was developed with  a classical timbre in mind, if you favor a brighter, more jazz or pop/rock oriented sound, the TIMBRE RICHNESS attribute may not necessarily reflect how well you're doing, especially if you're playing with a full sound in the higher range of the horn.

Otherwise, the 4 other attributes were exceptionally accurate, using either the built-in microphone of an iPhone 5S, iPad 4, or an external microphone (in this case one of Arthur Fisher's RM-5 ribbon microphone through a Focusrite Scarlett 2i2). Cortosia does a great job at leveling the loud audio signal coming into the built-in microphones of these devices, although the recordings sound better when you play a few feet away.

Cortosia will, no doubt, reveal some of your weaknesses, whatever level you are. Getting a great score, on all notes, at any volume definitely proved to be a challenge.

Swiping right in the Practice Room reveals the Time Domain Graph, where you can monitor 3 attributes: pitch, loudness and brightness. You're able to do this in real time, as well as when playing back the reference sounds, or your own recordings.

Regarding the reference sounds, each time Cortosia detects a certain pitch, it automatically switches to the equivalent reference sound, which you can play by tapping the instrument icon in the bottom left corner of the screen. Even though the app supports the whole range of the horn (concert C#3 to A5 on alto sax), reference sounds only cover concert D3 to D5. Scores will also only be used for computing ranks within that limited range.

Check out the video below, where I used the reference sounds to demonstrate both the Radar Chart & Time Domain Graph.

2. Metronome

Swiping left in the Practice Room reveals Cortosia's Metronome. It's very well designed and easy to use. The pendulum animation is very satisfying to watch, imitating the pull of gravity. Even if it covers just the basic functions one would expect from a Metronome, and won't replace a more complex, dedicated app, it is flawlessly implemented.

Check out the video demo below to get an idea of what the Metronome is capable of, and how intuitive using the user interface is .

3. History (Recordings)

You can access the History screen, where your recordings reside, via the treble key icon, on the top right of the Practice Room screen.

Recordings are sorted through one folder per day. Inside these folders, recordings are automatically sorted in chronological order.


Swiping right on one of the files reveals the upload and share menu. Not only can you upload recordings onto the website by tapping on the cloud icon, but you can also directly share on Facebook, via email and whatever app you have installed that supports the share function built into iOS.


You can also rename and delete recordings by revealing the menu with a left swipe

A note about uploading recordings to all recordings are moderated by musicians on the website, to check whether sounds are valid or not. This takes some time, so uploaded recordings won't show up instantly in your profile.

4. Practice Record

For some reason my Practice Record was reset in the middle of writing this review (my ranking as well). Although I divided my evaluation time between iPhone and iPad, there was just not enough data on the latter to do justice to this feature through my own screenshots or video capture.

However, this short excerpt from the official KORG promo video is a good visual representation of how the graph, and navigating works (if you'd like to watch the whole video instead of just the excerpt, please use this link: WATCH.)

The screenshot below, as well as the tutorial (which is covered further down in the review) should also give you additional insight on the feature.

Basically, the chart shows how much time you've spent each day on a particular note (the rounded, orange bars), and your best score as the red curvy line. You can swipe left and right to navigate through days, and tap the circled note, then scroll and choose which one to display.

Even though the implementation of this chart is well thought out, and data is easy to navigate, a few more ways to visualize progress would have been welcomed. For instance, a more global look, or the ability to view parameters separately (for example intonation) over the whole range of the horn, would be very helpful to pinpoint exactly what to work on to make the biggest impact on your playing. But this might just be beyond the scope of Cortosia, as the Radar Chart is main source of data.

As a quick note, when Cortosia becomes a universal app, it would be nice to be able to share data between devices so that the practice log remains accurate.

5. Ranking

Cortosia features a Ranking section, where the average score is positioned against other users. This was reset as the same time as my Practice Record (which makes sense). Still, the screenshot below should give yo a good idea of how the information is presented in Cortosia.

The app uses only the best scores for each note to compute your ranking. The global score is the average of the best scores for each note. If you obtain a better score for a certain note, this will be reflected in your score and ranking accordingly.

The only way to reset your score and ranking is to uninstall and re-install Cortosia, but as the app only uses your best scores, it would easy to override any unsatisfactory result you may have had when getting used to how Cortosia works.


6. Settings

This may not be the most interesting section of the app, but a few features are still worth mentioning, especially the "File Capacity" options. The way this works is that you can choose to allocate a certain amount of storage for Cortosia (or not at all). This is a very much welcomed option for owners of devices with limited storage.

The settings section also allows to toggle instruments, metronome sounds, as well as log in and out of your good-sounds account.


7. Information

This section contains a tutorial, under the "How To Use" button, and a link to the FAQ page on Korg's website.

Worth mentioning is how detailed and comprehensive the tutorial included in Cortosia is. It appears when you launch the app for the first time, but it is also available at any time in this section. The tutorial is so well put together, that reviewing alone is enough to get a very good idea of what to expect from Cortosia.

As such, please take a moment to look at the video below, which goes through each panel of the tutorial. Don't hesitate to pause and read the tooltips.


The Good Sounds website

When you create a good-sounds account (which you can do within Cortosia, or through the website), and choose to upload your recordings to the website, users can then vote on them. This does not happen directly; instead, if you'd like to help make ARTISTRY better, you have to navigate to the vote page, where a pair of (anonymous) recordings are presented for you to compare, and vote on.

On this page, you can filter what you'll be presented with by instrument and type of exercise. Listen to both recordings, then pick your favorite. After you've done so, you'll be presented with a checklist of the 5 attributes making the radar chart. Put a check mark on the attributes you think contributed to make one recording better than the other and hit "Submit". screenshot
Vote page

There are two types of exercises on note and scale. 

The first one asks the user to play a sustained note, trying to get the best possible score in all 5 parameters of the radar chart. 

The second one is unfortunately unavailable through Cortosia at the moment. The scale exercise looks at slightly different parameters than the note exercise, and the parameters that make up the Radar Chart in Cortosia. These are as follows:

  • ARTICULATION CONSISTENCY: the consistency of the transition between consecutive notes of the scale
  • TEMPO CONSISTENCY: the consistency of the rhythm tempo pattern used at every beat through the entire scale
  • DYNAMIC CONSISTENCY: the coherence of the loudness along the different notes of the scale.
  • PITCH ACCURACY: the correctness of the pitch through all the notes, measured as a combination of the distance to the correct pitch (according to the key and the pitch reference) and the stability of the pitch during the sustained part
  • TIMBRE QUALITY: quality and consistency of the tone through all the notes of the scale



It's fair to say Cortosia delivers on the expectations the app has set. Even though a few restrictions, missing features and bugs, come in the way of making Cortosia as great as it could be, it brings a game-changing technology to iOS, and promises even greater things in the future, as more features are added and ARTISTRY grows, and learns from user contributions.

Also important to note is the fact that Cortosia has been updated regularly since the app launched on the AppStore, each time bringing new features, or adding support for new instruments (case in point, the app was updated between writing this review and publication).

KORG Cortosia, the " Good Sound Tuner" is available on the app store for $9.99.

A big thank you to Morgan, Jennifer, James and Brian at KORG USA for their help and patience.



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