Have looked  at this and see it as something very helpful.
​Specially if starting out on guitar as it can get you to understand how solos work or how to make melodies. Or if being stuck just trying to get ideas.
​It is for guitar and more inclined for electric guitar work but could be used for sampling into other compositions or used for composing for other instruments as well.

Google Play:
play.google.com/store/apps/details?id=com.gyokovsolutions.guitarengineer
​
Guitar Engineer is a guitar riffs and solos auto-composition app. It helps composing guitar riffs and solos and accompanying harmony. No matter if you are a professional musician or just music enthusiast it will help you think out of the box and unlock your creativity.

This is extended version of free app Guitar Engineer Lite - https://play.google.com/store/apps/details?id=com.gyokovsolutions.guitarengineerlite

with many additional features:
- save melody and harmony as midi and text file
- change number of notes up to 64
- open saved melody
- many more scales 
- customizable guitar tuning
- change number of frets on freatboard
- natural harmonics and slide articulation
- EXPERT auto composer
- harmonize melody - auto compose new harmony over existing melody
- AUTO MODE - when this mode is active then composed melody is repeatedly played and auto composed every 2 cycles and the good melodies can be saved while listening
- transpose melody up and down

There are two methods for composition:
- manual - you select notes and chords
- automatic - using the AUTO COMPOSER that chooses "right" notes and chords.

The COMPOSE ALL app feature creates a new melody and accompanying harmony from scratch. You can use this feature as fresh ideas generator and then tweak the melody.


The notes, chords and note articulation are changed using the drop down menus for each note.

If you want to auto compose some notes of melody just check them and press Compose Notes button. Then the notes will be composed for you.

How can you use it:

At app start wait for all sounds to load. It takes about 15 seconds.
1. Select RIFF or SOLO mode, tempo, note scale and note length. 
2. Create melody rhythm by checking the checkboxes below the notes.
3. Press COMPOSE NOTES button to generate the notes for selected rhythm.
4. Listen to melody repeatedly and tweak the notes manually or with the help of auto composer by leaving checked the notes targeted for change .
5. You can select note articulation (muted/accented/slide/harmonics) using drop down menu on the bottom of each note.

You can play melody, harmony or rhythm by checking corresponding check boxes.

AUTO COMPOSER selects notes for these positions where the checkboxes are checked. If no notes are checked then melody is composed from scratch.

AUTO MODE - when active the melody is autocomposed every 4 (changeable in Settings) cycles. During playing you can save the composed melody via Save button.

Three types of AUTO MODE are available:

1. When AUTO MODE is active and COMPOSE ALL is selected then both melody and harmony will be autocomposed every 4 cycles. The text below button PLAY will show "AUTO ALL".

2. When AUTO MODE is active and COMPOSE NOTES is selected then melody only will be autocomposed every 4 cycles. The text below button PLAY will show "AUTO NOTES".

3. When AUTO MODE is active and COMPOSE CHORDS is selected then harmony only will be autocomposed every 4 cycles. The text below button PLAY will show "AUTO CHORDS".

The app manual - http://www.gyokovsolutions.com/manuals/guitarengineer_manual.php

Here are some videos that explain user interface. The videos are from Melody Engineer app, but the user interface is similar:

- Play controls - https://www.youtube.com/watch?v=94EJzS3xmkM

- Edit controls - https://www.youtube.com/watch?v=BypNdXy3Jso

- auto composing melody and harmony - https://www.youtube.com/watch?v=RFki1tDvtvo

- AUTO MODE - https://www.youtube.com/watch?v=C6y2VNgFpCE

To get the full app (The Google Play version is not the full one) you have to get it through Amazon... They say that it is easier for tax declarations or something suchlike? But it does make it harder for the customer that does not want to sign up for one more appstore...

Google Play:
play.google.com/store/apps/details?id=com.gyokovsolutions.songengineer

Song Engineer is an app for songs auto-composition. Just press COMPOSE and you have a new song. You can listen to songs and save them as midi file. The app can provide you with song ideas that you can develop and enhance.

Hear some sample songs here - http://www.gyokovsolutions.com/SongEngineer.html

This is the full version of Song Engineer Lite with many more features - https://play.google.com/store/apps/details?id=com.gyokovsolutions.songengineerlite

Full version app features:
- select song tonality
- use different song elements (INTRO, VERSE, PRE-CHORUS, CHORUS, BRIDGE, OUTRO)
- change song element length
- rearrange elements
- change song elements root and scale type (major, minor, pentatonic, blues, chromatic)
- recompose individual song element
- change instruments used in midi file

How to use:

1. Select song tonality using TONALITY drop down menu
2. Press Menu - New Song. New song in chosen tonality is created. Optionally you can change song structure using the three dots button on the left side of every song element. You can change element types, add new elements or rearrange them.
3. You can change the elements (VERSE, CHORUS etc...) scale root and type(major, minor, pentatonic etc...) that will be used for composing, change the element length (in bars). Only the first occurrence of every element has the controls unlocked. When you change some property then all elements of the same type (VERSE,CHORUS etc...) will change their values accordingly.
4. Press COMPOSE
5. The song is composed
6. Press PLAY to listen to the song. You can change song tempo. Also you can hear every element and recompose it using the three dots button on the left side of each element. Also you can include or exclude instruments(lead, harmony, bass, drums) using checkboxes.
7. Press SAVE to save the song in midi format. Song is saved in [sdcard]/SongEngineer folder. In settings you can change default instruments type used in midi file.

Brian Eno is someone that is interesting as a person and also credited with being the originator of Ambient music did one app/music release called Bloom in the early days of mobile apps but alas only for iOS which hurt...
But now there is a improved and expanded and we have Bloom:10 and it sounds promising.
​The video is good  to hear what the creators have to say about this.

Google Play:
​play.google.com/store/apps/details?id=com.opallimited.bloom10worlds&pcampaignid=MKT-Other-global-all-co-prtnr-py-PartBadge-Mar2515-1

Brian Eno and Peter Chilvers are pleased to announce Bloom: 10 Worlds – a developed, augmented and expanded new edition of 2008’s game-changing original Bloom app, which explored uncharted territory in the realm of applications and was dubbed “The First Great iPhone App” by Gizmodo.

Requiring no musical or technical ability, the egalitarian and user-friendly Bloom app enabled anyone of any age to create music, simply by touching the screen. Part instrument, part composition and part artwork, Bloom’s innovative controls allowed users to create elaborate patterns and unique melodies by simply tapping the screen. A generative music player took over when Bloom was left idle, creating an infinite selection of compositions and their accompanying visualisations.

Bloom: 10 Worlds is a reimagining of the original – not simply a remaster. If the original Bloom was a single, then this would be an album. The widely broadened palette of sounds and images can be experienced via 10 new ‘worlds’, each exploring a new direction for Bloom. The first world the user encounters is an echo of the original app, with circles appearing where the user taps, while the later worlds each introduce new combinations of sounds, shapes, colours and rules of behaviour.

Please Note: At present an audio issue exclusive to the Google Pixel has prevented us releasing on those devices. We apologise for any disappointment, and hope to resolve the issue in future.

Praise for Bloom: 10 Worlds

"Few apps are truly iconic. Bloom was, and now its story lives on in this impressive and necessary follow-up." Stuff TV


Praise for the original Bloom

“The very first iPhone apps were universally dull. And then Bloom came out. It was immediately obvious that something special was happening. The app was interesting on an artistic level – one that made you reconsider the relationship between technology and music. It raised the bar for musical iPhone apps.” Gizmodo

“Hypnotic and ludicrously addictive.” The Guardian

“A relaxing alternative to just about anything else you can do with an iPhone.” Wired

Brian Eno – musician, producer, visual artist, thinker and activist – first came to international prominence as a founding member of Roxy Music, and immediately followed with a series of critically-praised, pioneering and influential solo albums – including the soon-to-be-reissued Discreet Music, Music For Films, Music For Airports and On Land. His visionary production includes albums with David Bowie, Talking Heads, Devo, Laurie Anderson and Coldplay, whilst his long list of collaborations includes recordings with John Cale, David Byrne, Grace Jones and James Blake. Equally notable are his highly-acclaimed visual experiments with light and video, which have been exhibited all over the globe – from the Venice Biennale and the Marble Palace in St. Petersburg to Beijing’s Ritan Park and the sails of the Sydney Opera House. 

Eno began collaborating with musician / software designer Peter Chilvers on Will Wright’s computer game Spore. Their shared interest in generative music rapidly lead to the development of a prototype for Bloom in 2008. In the intervening decade, they experimented further with the field, expanding their catalogue of apps with Trope, Scape and Reflection. In that time Chilvers has also acted as an engineer and technical advisor to Eno on a number of other projects. A series of multi-speaker installations around the world laid the groundwork for 2016’s The Ship, and they premiered Bloom: Open Space, a mixed reality installation in Amsterdam in 2018.

In addition to his work with Eno, Chilvers co-founded the Burning Shed label and online store, toured with Underworld’s Karl Hyde as keyboardist and musical director, and has recorded instrumental albums and collaborations with vocalist Tim Bowness.

Made with Wotja and it shows how this would be for a good app for anyone that need a lot of music generated for stores, restaurants, films or for vlogging etc. without having to know composing/producing.
Unfortunately you need to get it through Amazons app store if wanting the whole app and not just the demo...
Anyway it is also available for Windows and Mac.

Youtube description:
Each track is infinite and sounds differently every time you press PLAY. Used functions: slow (subsonic) LFOs, probabilities, random notes and controllers (pattern effects 20-29), random phase setting at the beginning of the song, random interpolated waveform of LFO, prime numbers as the sizes of parallel patterns (in the set of MetaModules), etc.

Demo songs + sources + online JavaScript SunVox player:
warmplace.ru/soft/sunvox/jsplay/

One of the pioneer developers of generative music software with even Brian Eno releasing music using earlier software in the early 90's.
​(Read interview for more information regarding how it started).
But now the software is released under the Intermorphic label and it just turned ten years.
For Android there is only one app but a deep one with a modular synthesizer engine and many tricks up its sleeve, the app being Mixtikl.
In either case here is the blog post they wrote for their ten years celebration:

https://intermorphic.com/blog/posts/170109-Intermorphic-is-10-today.html

To read this recently published in-depth interview made by Ashley Elsdon (Palmsounds) go here:

https://palmsounds.net/2016/12/31/lets-finish-off-2016-in-generative-fashion-an-interview-with-tim-from-intermorphic/

This music made with the funky app Kosm!
It is one of my favorite apps and it just got a update making it even greater.
For free and without publicity...

The latest update:

changes for version 2.0.2:
- added reset mode for clearing all orbs
- added support for small screens
changes for version 2.0.1:
- implemented low latency audio engine
- implemented high resolution graphics
- optimized UI
- removed the previous two minute limit on recordings
- greatly improved the writing speed of saving the recording

Personally do not understand how this application has managed to get so much attention and even won ten thousand euros in the Appart awards, try not to criticize applications  but think that this app shows how far an app can go with a nice interface and right promotion and having not much of real content.
Maybe it is something that I missed and please someone prove me wrong and send me some music that is half decent even if it is just 20 seconds or so made with Geometric music...
musicalandroid@yahoo.com
Anyway here is three more websites talking / mention it and one of them being Wired plus a mention on CDM which are a pretty big deal for a half assed app!
http://www.wired.com/2014/08/a-clever-app-that-lets-you-make-music-with-shapes/
http://createdigitalmusic.com/2014/08/quicker-interfaces-make-sound-widely-used-apps-geometric-music-waved/
http://nymusictech.com/geometric-music-app-beats-with-shapes/

It is for free and without publicity so if you are curious:
Geometric Music

Intermorphic release this Tikl pack to use for Mixtikl for free:
____________________________________________________________________________________________________
Morphing Drum + Bass ("MDB")

• Requires Noatikl 2.5 or later or Mixtikl 6 or later.
• This is a fun "retrospective" generative Tiklpak of the 1998 SSEYO/Zero-G title "Koan Essentials Morphing Drum + Bass" ("MDB").
• It comprises the 77 MDB SF2 files (22kHz, mono, created back in 1998 from loops and samples owned by the awesomeZero-G) and the 100 MDB generative Koan SKD templates that referenced them (but converted to Noatikl templates). For Mixtikl users it also includes 4 new demo Mixtikl mixes to give a quick flavour of what can be done when you include some of these SF2 in a mix.
• Zero-G have kindly allowed us to make the MDB SF2 available for free in this Tiklpak! To show your appreciation, please do visit the Zero-G website

____________________________________________________________________________________________________
So to download this go to:
http://www.intermorphic.com/tiklpak/download/

Okay now this is going to sound confusing as things are slightly complicated with this new version of Mixtikl as there is now a Google Play store version and one for Amazon that have different versions plus that the Amazon version have different options for in-app purchases...
They have already got some critique for this but it is not so bad if you want what i would consider the best and most flexible Generative music app you can get for Android.
The biggest news in this update is that you can load SF2 files. 
It comes with six of them preloaded. 
It is also the first time it is available for the Google Play Store.

Before I go into the differences in versions etc.
You can still buy Mixtikl 5 on the Amazon Play Store and it recently got updated but there will be no more updates. So if you have it and do not find the new functions interesting it can be an idea to continue to use the number five version until devices do not support the older version? 
Okay So the Google Play Store version is for free and supported by ads. It does not have drop outs every ten minutes like the free Amazon version and you can use the save function.
What it does not have though is the possibility to buy the in-app purchases which are:

Save / Export / Clipboard / Mix Recording / No Timeout 1.46 € / 1.98 $
Remove ads 0.73€ / 0.99$
Sound / FX Network Editing 1.46 € / 1.98 $
Generator Editing 1.46 € / 1.98 $

Ahhh so to get the goodies you still have to sign up for Amazon...
But it can still be good enough with the free version for the Google Play Store version as you can save and it does not have any drop outs in the sound?

It is a little bit weird to confuse people with two different versions and on top of that having version 5 separate from number six but it is still a very interesting application as you have in number five and in six (with the in-app purchases) a full modular system built into it and a lot of ways to shape and create how you want the music to be generated. 

There is a Desktop version to that is and as far as I understand the same, meaning that you can interchange work in progress. It is actually so much functions that it would take me too long to write about it now but there is a lot of information on their website and there is a lot of videos on Youtube where you can get a deeper idea of how it works, so far only for 
Mixtikl 5... Here is one that gives you an idea.

Google Play Store version:
Mixtikl 6
Amazon Play Store version:
Mixtikl 6
Link to the homepage with all the features listed:
http://www.intermorphic.com/mixtikl/

I do hope that the developers have not made themselves a disservice by this confusion as it is a good, stable application and the developers have always left me with a good impression... 
but in the end it is not too complicated and the only hinder I can see is that you still have to sign up for Amazon to get the full version without restrictions as many prefer to have just one account for application purchases...

This application was made by a Boogie Woogie piano player and that fact is maybe more interesting than the app in itself... (at least to me).
It is automatic midi generator for melodies/songs with the usual suspects for manipulating the direction you want the music to go in. But as you can hear in the video it sounds like a  lot of notes being spit out making it like a music experiment from a avant garde composer 
of the sixties... Which could be just what you want!
-----------------------------------------------------------------------------------------------------------------------------------Midi based musical pattern creator with special algorithm that produces more than
300.000.000.000.000 different musical patterns.
Easy to handle, only few clicks and drags needed.
Multiple usage: Composition, ringtones, jingles, game sounds, melodic patterns, ideas for songwriters, ear trainer, polyrhythmic patterns ... or just for fun!
Including individualized scale designer: from chromatic scale to gamut to freely designed scales.
Choose between 128 free and resource friendly MIDI Sounds.
Export function: Export your Session to MIDI file for further use in DAW (Digital Audio Workstation).
Create patterns from one second to several minutes duration.
-----------------------------------------------------------------------------------------------------------------------------------

Of course we also have to listen to the developer play some piano!

Play Store link:
Pattern Composer

A very good looking Automatic Sound Generator that has one obvious difference compared to other Automatic Sound Generators (If anyone have a better term for these type of apps please let me know in the comments...) It uses real instrument sounds instead of the standard blips and blops like in for example Nodebeat. Have only tried the demo but it seems stable and if you push it you can get interesting music out of it. The limitations are maybe that if you want to use the drumbeats that are included there are not too many of those but then again it can be used perfectly well without drums to.
You could use it for getting some ideas or for building songs with it as help but think that the strongest use for this application would be for jamming and you do have six different chord progressions (or none) that can dictate the flow of the music plus the notes that you choose for each generator and some other parameters like Bpm for example.
This could actually also be used for restaurants / stores etc just puttering away as it does changes over time and sounding pretty nice why not?
Here is some videos and there is more videos / information at the well done website.
My favorite must be the soft disco song that the developer used as one of the demonstrations.

Playstore link:
Acccelerando
Website:
http://www.acccelerando.de/en/