Okay so the other day posted about a small but nice little app called rainstick. This is the same developer but this app is part of a bigger project that is very interesting that have been written about before here but this is a good reminder.
So this app is a new addition to something that the developer calls Puredata Party Publisher and that is a gang of apps that can play together through Wifi tight and syncronized.
Not only this but on the website there is information how to do apps for Android using Pure Data and also they want people to get involved.

What is great is not only that the apps are good but it is all for free and without publicity!
 Personally I am happy that the project is continuing plus that the developer is doing other apps as well as I like what he has been doing before and lately been missing some of the smaller quirky Android apps (the apps that are outside of this bigger project) that was pretty common place two years back.

Website to read about the whole project:

http://b2renger.github.io/PdDroidPublisher/

Google Play info:

PPP-LooperSynth

PPP-LooperSynth is meant to be used with other PPP instruments.

PPP-LooperSynth is a polyphonic synth coupled to a hexagonal keyboard layout. The controls allow you either to play it like a classic keyboard, but it can also record the notes you play in a 16 step sequencer and play them back as a loop. 

PPP is a framework offering to support midi jamming over wifi features to audio applications and instruments. That means that apps can be connected to each other over wifi with a slave/master paradigm, enabling each sequencer to be in synch with each others. It can of course be used as a standalone sequencer. More here : http://ppp.mgsx.net

When it comes to collaborations there starts to be some options and this is a "new" one.
It seems like a nice and cloud based application that can be used for recording ideas or to make some more serious recordings to work on with other musicians as one of the main ideas is to  easily communicate with other musicians. Unlimited storage for tracks sounds pretty good and it comes with a mixer.

Here is a article of it by Performermag:
http://performermag.com/instruments-and-gear/recording-gear/software-recording-gear/how-bandlab-is-changing-cloud-based-recording-collaboration/

Google Play info:
BandLab is the cloud platform where musicians and fans create music, collaborate and engage with each other across the globe.You can capture all your musical ideas seamlessly and develop them with others anytime, anywhere. Your creative workflow has never been more efficient and productive.
With BandLab, creativity has no limits!
CAPTURE INSPIRATION:
• Capture, store and recall your song ideas wherever you are, wherever you go.
• No more misplaced post-its or lost voice memos. You’ll never lose an idea again.
• Synchronised to all your devices through the cloud.
DEVELOP YOUR IDEAS
• Develop your ideas into songs - alone or with musicians from anywhere in the world.
• Collaborate on multi-track projects without worrying about the tools with our built-in Mix Editor.
• Follow your creative process wherever it takes you with our visual version control system.
SHARE AND ENGAGE
• Invite other music creators and lovers on your creative journey.
• Share unreleased versions and work in progress for feedback.
• Pull back the curtain and forge a deeper more meaningful connection with your fans.

WHAT'S NEW

• Embedded links in Chat! The most convenient way to share Songs and other musicians profiles with your friends and bandmates. Also, it is a great way to start conversation with others ;)
• Small but very important UX update. Song Tree View now shows if a new version of your song is synchronized with the cloud.

Groovecloud the sample based sequencer based collaborative application will soon introduce the Grooverse overview off the collaborative projects and I guess they would be clickable.
Think that the images speaks for themselves.

The Songtree application is still in Beta but you can sign up here and start to use it already
https://play.google.com/apps/testing/com.ntrack.songtree

They also have a page dedicated to some of the collaborations. Do think that this can be a major outlet for people that play real instruments as is heard on some of the tracks that are highlighted. It can also become a excellent way to find musicians or to take basic recordings of your own to let them grow into full songs and lead into unexpected places.

Was a little bit dismissive when reading about Songtree at first but having heard some of the high lights and seeing it for more of a outlet for real instrumentation and not electronic meanderings that go nowhere, I now see the possibilities. 
Now just need to send some acoustic guitar tracks into the Songtree eco system and see what happens!

To hear the highlights and grok the full impact that is the idea of Songtree go here:
http://songtr.ee/highlights

So Groovecloud is a application that you can use for creating music in real time with people all over the world and that is a funky thing!
Here is just a short video while one of the Groovecloud developers are checking out someone somewhere doing a beat...

This application has been in Beta for a while now and it is slowly creeeping up to something interesting. 
If you missed this here is the Play Store description:

 NOTE: this product is currently in open beta. We'll collect system information if the app crashes. The free app lets you start up to 8 projects on GrooveCloud, or interact with other projects without any limitation. If you start a public session, you agree that random users could edit it.Make music with your friends in the Cloud!

GrooveCloud is a collaborative music sequencer for the Android platform that enables its users to make music together, at the same time. For example, imagine yourself arranging a drum pattern while a friend is taking care of the bass section, and while someone else is arranging or mixing the track.

The audio engine offers the following features:
-song arranger with 8 patterns of length (1-2-4-8 measures) 
-up to 8 DRUM samplers with ADSR envelope, LP and HP filter.
-up to 8 INSTRUMENT samplers, with ADSR envelope, LP and HP filter, root note and musical mode selection.
-per-note fine tuning of envelope and filter parameters
-mixer section with pan, delay and reverb sends.
-export to OGG
-more then 200 free samples

GrooveCloud was designed to respond to a specific need: having a musical sketchpad with a "cloudy" feel. Indeed, it offers a number of social features, like:

-song information is stored in Online Servers and is available almost instantly to all the song participants.
-all the manipulations made by any of the participants are propagated in few seconds to all the other participants
-users can export the song to the Community Services and post a link to the audio render on Social Networks.
-users can review the latest edits.
-users can invite friends to join the song by email.
-songs can be either be public (editable and viewable by anyone) or private (editable and viewable only by the creator or invited users)