This is not really a music app...But as there is a softspot in my heart for brutal metal and it is now for free/sale felt that it needed some attention.
​It looks brutal but fret not if there is anguish watching blood shed as it is all pixelated gore.
Do not play much games (or not at all, my patience is lacking...) but think this will be experienced tonight...

Google Play:
play.google.com/store/apps/details?id=com.sinsquid.brutalbrutalness&referrer=utm_source%3DBlog%26utm_medium%3DApp%26utm_campaign%3Dsale

A Heavy Metal game about retrieving the missing band-members from a brutal world of death, destruction and evil creatures. You must fight your way through 30 levels, beat the bosses, get weapon upgrades and die brutally many times.

Theme song from Novembers Doom
30 Levels
3 Boss fights
And a brutal soundtrack containing lots of Death Metal and Heavy Metal

The guy behind iterationGAMES was posting about his games and his use of the SunVox engine in all of his games and could be something for game developers to have in mind if looking for a fast, reliable and small music engine for games and applications. 
To read more and to check out the games go here:
http://jph_wacheski.itch.io/
http://iterationgames.com/

Not much of a music app post but as it is something that have excited me since Virtual Reality finally is getting here after Oculus Rift got announced a year ago or so.
God damn it I have been waiting for this since I tried a very basic Virtual Reality game with headset and tracking of movement in a amusement park at the end of the eighties. 
At the time reading Cyberpunk books obsessively and expecting it to be just another year or so to be flying around in all kinds of environments!
So it just took 25 years more until it finally is happening.
The problem being broke and it is going to take some time until I can get my hands on some Oculus rift glasses or the Sony version. 
Luckily enough there is some alternatives already and one of them being cardboard glasses that you can make yourself! 
It is surprisingly simple and there is a lot of room for your own inventiveness to modify or do your own design.
There is also to my surprise a bunch of apps to go with them. 
There is also two other cheaper glasses that you can buy.
Not only for games have been reading of a lot of different artist projects being made already and this is just the beginning. It is funny that just a year or so before Oculus rift got announced William Gibson wrote a novel taking place in the near future that had 
Virtual / Augmented reality used as art projects where you overlaid reality and 
being able for example see historical death scenes etc. 
Actually it is unlimited and games are probably going to be the least interesting aspect?
What this is going to mean for music making is not clear yet but one thing is to be able to visually be in the same space rehearsing, controlling Virtual entities on stage and at the same time be there on stage virtually or playing virtual instruments in the air for example. Something that already exists is virtual classes where you can overlay your own hands on top of the teacher.
Well this could easily turn into rambling without end so it is better to end it here and just post a video from Google talking about their cardboard glass project and then post links for further exploration.

Links:
Google Cardboard page
Google Cardboard app
Refugio 3D glasses
Durovis Dive Glasses

I wish that this was available for Android but unfortunately it is not.
But think that it is interesting enough to report anyway as it just came out and I have been following the development of this for some time now.
The idea of the game is that you explore and put together broken parts of 
"machines / synthesizers" to be available to use them for making music in the end you are able to use it as a multi track music program but looking like zillion times cooler than any other music making program out there!
It is cheap around 14€ / 19$ and have gotten good reviews...The sadness though for me is that my PC is not strong enough to play the game... buhu.

Link to website:
http://fractgame.com/images-and-videos

So this year have heard so much professional music being made with Android music applications, some being released for film and here is one track that got released for a commercial video game. 
It must be just out of ignorance / laziness that there is people that deny the possibilities of Android and the music applications that exists... 

To read more about the game:
http://minotaurproject.co.uk/txk/

Do not play any games anymore but maybe this one while waiting for the new Nanoloop.
It is a funny idea and it looks well executed.
Their other games looks interesting to as they have a look to them that you do not see elsewhere... Maybe have to play a some games after all.
Guess you have to see the video as that explains it much better than I could.

Playstore link:
Chiptune Runner