Obviously based on the TB 303. For free and with a limited sequencer that seems to be planned to be expanded in a future paid version.

Google Play:
play.google.com/store/apps/details?id=com.rockrelay.synth.bassline

Square and Saw oscillator
Step sequencer
Midi support

There is some apps that are very interesting and good but that never seems to get the attention that they deserve... This one with less than a hundred installs are one of those.
The concept is good and well executed and the sound is mighty fine. The basic idea is that to manipulate and modulate the parameters selected by tilting the device in different ways.
Plus it comes with a sequencer.
Another mobile app that if coming out as hardware would have been mentioned and written about in many a big music sites/magazines.
So just forget all the unnecessary clutter of your device as the phone part and Facefuck  and just have Fang synth installed and there you go, a new exciting hardware synthesizer that can do something no hardware synthesizer can do!
The look may seem crude but personally it entices my sensibilities to inspiration as do his other excellent and most brutal drum machine on Android, Dragon.

The new video does not do it full justice sound wise and does not show you that there is a whole lot of deepness to swim in, that can be slightly overwhelming before coming to grips with it.
Not too much though but enough to keep you occupied in sound sculpting and ideas for a loooong time.

Google Play:
play.google.com/store/apps/details?id=com.thiiird.fang

​The update:
Sequence can be changed from any page
Each step of a sequence can be triggered after the piano roll to allow for chord pads
Notes to the arpeggiator will wait for the next step instead of beginning timing at the first note on. Old behavior can be restored with the control named Independent time
Probability functions for pitch
New oscillator wave types
New presets viros, DSLIME, Carnival, sn, further down, wobble, and Hethodic

So posting this as this synthesizer/watch thingie will be coming with an Android app to expand on its possibiities.
It is a weird thing reading about it as there is a lust to have such a thing but to be honest would probably never use it more than once or twice and a smart phone is more flexible in either case... plus that it is going to be kind of expensive (450 as early bird on Kickstarter) which really kills any lust for a big watch mini synthesizer.
But there is something funky to it anyway and it would for sure work as a conversation starter and a lot of people would think you must be an annoying hipster idiot!

To check out the Kickstarter:
www.kickstarter.com/projects/synthwatch/audioweld-synthwatch-worlds-first-wristwatch-synth?ref=nav_search&result=project&term=synthwatch

Nice that there is already integration for some midi controller!
There is a couple of apps out by this developer and they are all low latency.

From Youtube description:
Advanced midi support in the android app Analog Synthesizer by rockrelay. Tests on android and Xiaomi Redmi 5 with Novation Impulse 61 Arturia Keylab and Access Virus Ti2 as a master midi keyboard. Perfect midi support of multiple midi devices.

play.google.com/store/apps/details?id=com.rockrelay.synth.analog

There is a lot of small funny toys now for anyone with some extra cash...
These looks like they could be fun and the app provide a lot of control that would have been hard to fit into such small machines otherwise...
Myself have been snared into toyland and have a small drum machine -tek.Drum and in the end got a Volca Bass for a good price second hand. 
So it is nice to have these things around as they provide some inspiration.
How much they actually gets used in the end is something else...

Google Play:
play.google.com/store/apps/details?id=com.modalelectronics.craftapp

The developer have an interesting set of Android apps and had this installed on an older now defunct mobile. So was going to install it again and now there is only two of the apps on the Google Play store and this one is not there anymore.

​Still listed/written about on their website as well as the other apps not on Google Play...

Will ask about it, can imagine that it is temporary... or maybe he decided to take away the free apps that came with ads?
The mysteries of developer and Google Play thickens...

This is a gem and discovered it on Friday and yesterday starting to record beautiful noise.
It is made for more noisy happiness but there can be some melodic things coming out of it as well.
There are no clear controls but buttons to push and activate two oscillators and a whole lot of parameters underneath it all. Which you can use to spawn variations plus that there is two more windows that can be used to further affect the chosen patch.
Then there is things like a up to 30 seconds of sounds shifting from one patch to another...
Actually it is much better to try the free version instead of me talking about it or if you like some useful noise just buy it straight up for just one money.
Trust me it is worth it.

It is easy to use but to get the most of it is recommended to read the manual...

Really like this app and think that the developers made a wise choice in making something that would be very complex to build up with every control available to something more fun and exploratory without sacrificing the results in the process...

Will work more with it today having fantasized for some time now about doing more noise oriented pop songs and was going to use Noise Machine as a basis but with MendelTone as a second application there can be some serious damage made. 
They complement each other beautifully having very different vibes but still keeping in the noise domain.
And yes there is no record so to fully compose with it, something to record into is a good idea...
​I am using SunVox on PC for this project which with the SunVox sampler/s is working out real fine.

If you make any music with MendelTon, please let me know...
musicalandroid@yahoo.com

Google Play:
​play.google.com/store/apps/details?id=com.darwinarts.mendeltone

Manual:
www.darwinarts.com/doc/MendelTone_1.4/user_guide/

MendelTone is a portable sound evolution app. The MendelTone synthesizer is a virtual modular synth optimized for mobile platforms, and features a flexible patch topology with basic modules such as oscillators and delays.
Using a proprietary variant of the genetic algorithm based loosely on the work of Charles Darwin and Gregor Mendel, this app allows you to search the space of possible synth tones using preferential selection and patch breeding, and hear the results in real time.

The developer/s have been involved doing one OSC app for Android earlier and seems like an interesting bunch of people/s. This latest offering is a VSTi that is made for generating more droney type of sounds and it sounds interesting but they also developed a controller app for it.
What strike me is that they only did it for Android. 
Picking up the general vibe from videos seen some months ago it seems to be because of idealogical reasons and I can certainly identify with that!

So here is the website with a whole ot of more information regarding the VSTi:
​oceanswift.net/aeolianmeditation/


Google Play:
​https://play.google.com/store/apps/details?id=c.oceanswift.aeolianmeditationcontrol

CONTROL Ocean Swift Aeolian Meditation with your Android phone or tablet!!!
Aeolian Meditation Control lets you control the Aeolian Meditation VSTi and or standalone synthesizer using your phone or tablet with full bi-directional control capability. Every parameter on the device is represented on the app, as well as enhanced functionality such as XY pads and randomizers..

for either bi or uni directional control of the Aeolian Meditation VSTi or standalone device from any Android phone or tablet.

VSTI & STANDALONE ADDICTIVE SYNTHESIS
Aeolian Meditation is a complex additive synthesizer with a unique a-symmetrical design capable of generating unique and beautiful melodies, meditative and hypnotic tones, movie and game and musical soundscapes… Where the only limit is your imagination

Features

MODULATE EVERYTHING
Aeolian Meditation features intricate and powerful modulation capabilities where everything is modulated by dedicated controls, evolving in free rate or in sync with the project tempo. Volumes, frequencies, filters, effects – sound emerges and flows in magical directions.

POWERFUL FM CAPABILITIES
The FM especially allows for out-of-this-world sounds.
Not only can you toggle the FM source from midi to a set note to a frequency knob, the FM also utilizes dedicated modulators that tweak the source frequency and FM depth.

MULTIPLE SOURCES
Play it like a monophonic synth or morph your vibes to strange and magical planets by switching to note or frequency based drone mode

A VARIED AND COLORFUL EFFECT SECTION
Effects section featuring reverb, delay, chorus, reducer and filter.
Endlessly sculpt your sound beyond the initial synthesis.

This app was pretty nice some years ago specially as there was not too many good apps competing but there was no saving so it was a little bit sad as personally did not feel much interest in spending time to have the work lost when closing the app...
Well I missed that there is now a Pro version that came out some months ago. with saving.
So it is nice for anyone that likes a nice beat box that is simple to work with and it does only cost two monies!
The free version is also still available to test...

Google Play:
https://play.google.com/store/apps/details?id=com.vtrsoftware.pureSynthPro

Vintage additive music synthesizer

pureSynth consists in four additive synthesizers plus one beat generator controlled by a five grid sequencers.

Synthesizers:

It's possible to save parameters of each synthetiser and load them individualy.

There is a view to control all parameters of all synthetisers and beatbox easily.

Each synthesizer has six oscillators to generate the fundamental note plus five harmonics: second, third, fifth, seventh and ninth. The oscillators can generating a sine wave, triangular wave, square wave and sawtooth wave. 

In order to control the notes pureSynth has an envelope controller which controls the attack time, decay time, sustain time, release time and sustain level.

It's posible to clear all marked notes pressing reset button(long click).

The note range accessible from the pad is controllable dragging a finger over it vertically. From midi note 12 to 84 is possible (7 octaves).

One LFO modulator is included in each synthesizer, it modulates the signal from 0 Hz to 20 Hz.

There are two sound effects possible: distortion and delay.

BeatBox:

Reproduces up to 12 sample beats and the volume of those beats can be controlled by separate. Those beats are: bell, block, clap, cymbal, hat, 3 difference kicks, misc, shaker and snare.

Sequencers:

There is a view to visualize all sequences of all sequencers where you can activate/deactive each sequence by separate.

Sequencers go up until 16 sequences of 16 steps. 


The main menu includes a three ways equalizer, BPM controller(from 25bpm to 200bpm), ON/OFF button and controls to record the audio output(all files are stored in pureSynth folder in sd card) which you can share with your contacts.

The developer has made one unique drum machine called Dragon and one Drone synthesizer called Wiisp. This is the latest app and is focused on using the motions sensors in a device for controlling a shitload of parameters.
Each parameter can be controlled by desired amount back n forth and sideways.

It really is worth spending some time with it to get out as much as possible from it.
Think this will appeal to people that are not afraid to take some time to find the sweet spots and some will be confused and run for shelter in more conventional music apps.

Yapps just like his other apps the graphics are bare bones which will scare off some but personally I find appealing, as it fits with the rawness that can be made sound wise.

Google Play:
play.google.com/store/apps/details?id=com.thiiird.fang

Fang is a synth app based on motion modulated control through accelerometer information. Each parameter can be linked to different directions of motion. Contains presets, WAV recording, a stepped arpeggiator with diatonic scale locking, a multi-pattern sequencer, wave shaping oscillators, resonant filter with envelope and pitch following, and an effects rig (including formant (vowel) filter, pitched delay, reverb, down-sample, bit reduction.) Capable of strange sonic textures, complex evolving arpeggios, or classic sequenced synth sounds.

Notes are generated with a sequencer and keyboard. The sequencer works by moving a step at the rate specified. There are four patterns that can be played and edited independently.

The keyboard has a set of notes that can be played or buttons which hold notes. Held notes can be cut off by sequencer notes and play notes of the same pitch.
The arpeggiator receives notes from the sequencer and keyboard. Its rate is controlled by both synced time and ms that are added together. It has variable steps, step transpose and gate. The steps and timing can be reset periodically with the optional arp reset. There is optional diatonic scale locking as well, allowing you to select a root note and scale from major, dorian, phyrygian, lydian, mixolydian, minor, and locrian.

The synth's sounds are generated with five voices, each with two oscillators that modulate between triangle and saw. Modulation is effected by an envelope. There is a pitch envelope that effects both oscillators. The oscillators are capable of fm (osc B modifying osc A.) Both oscillators can have their signals sent to the filter or directly to the amp envelope. A white noise signal can also be added to the filter or directly to the amp envelope.

The filter is a 4 pole resonant band-pass whose frequency can follow the pitch. It is also effected by its own ADSR envelope. The filtered and unfiltered signal is sent to a per voice down sample and per voice delay under synth menu. All voices are sent to an effect rig with a formant (vowel) filter, pitched delay, reverb, and bit reduction. Presets and WAV files are stored at /device root/fang/.


Four sub parameters for each parameter to adjust left, right, back, and forward accelerometer input
Save and load presets
Export audio as WAV (exported to /device root/fang/)

4 pattern 8 step sequencer with adjustable rate
Stepped arpeggiator with sync and ms rate control
Diatonic scale lock

5 voice polyphony
Pitch envelope
2 oscillators wave shape between triangle and saw by slider and by an envelope
Oscillator B to A frequency modulation (fm)
White noise generator
Per voice delay
Per voice down-sample effect

4 pole resonant band-pass filter with frequency control by slider, pitch, and ADSR envelope 
Amplitude controlled by ADSR envelope, number box, and pitch

Reverb
Formant (vowel) filter
Delay with re-pitched feedback
Bit reduction


File permission is for presets and WAV recording. Would love to hear anything made with Fang, email is posted.

The new update of Noise Machine is not the biggest but an interesting one.

To pay for the premium version you do to get rid of the ever so annoying publicity that are a regular feature of many free apps but it also gives access to a sequencer.

If this would have been a more standard music app it would not have been too exciting, but Noise machine being focused on getting synthesized noise out of it. Being able to set different types of noisy oscillators, Lfo (different types) modulation, filter, delay and distorted ring modulation it can bring forth a whole lot of different flavors of noise.

This may not be obvious at first glance as the interface appears simple but rewards tweaking, with all kinds of goodness for musicians that are willing to step out of the comfort zone of commonly accepted norms.

Ahh so back to the sequencer… It is a simple sequencer but very useful as each of the sixteen steps can be programmed with one setting of noise. Making it possible to build rhythms of noise that would be hard to achieve without much more work in other ways.
There is also the added bonus of randomization of each step for the lazy ones. Giving way to unexpected surprises of course.

There is griones, always griones knocking at the door of perfection!

The most obvious one being that there is no way to save the sequenced pattern steps. So once the app is turned off… But it comes with internal recording for further chopping in an audio editor or for importing into other apps/programs.

Another thing that could be nice is to be able to see what Bpm the sequencer is set to.
So that is something that has to be set by ear or retro fitted later into wherever the recordings go later, if wanting to use it within music set to a specific beat.

Would love to see this concept taken farther with more tracks, effects etc as it is unique to be able to noise things up on an even deeper level!
Maybe the closest to (but not limited to noise generation) that is Grainstorm which I also recommend to check out. Grainstorm can also load sounds so it is a nice companion to Noise machine…

A nice little ad free freebie.
Does not do much and a lot of people will dismiss it for the reason that it is not easy to not what notes are being played if any. Manipulatign the sound with fingers on the screen and with a little bit of play interesting textures and notes will find their way out.
An app to sit and record to later cut up for samples.
There is plans to add more control over this app later so even if it is not being used it can be a good thing to install to be aware of updates in times to come.
Who knows could turn into something unique as it is off to a good start.

Google Play:

play.google.com/store/apps/details?id=ca.dumbcomics.experimentalfmsynthesizer

Create complexly bizarre sound effects and intellectual experimental music.

Move some of your fingers around the screen, and listen to the sound transform. Learn about FM synthesis.

Annoy your teacher. Annoy your friends. Annoy your mom. Annoy your neighbour's dog. Annoy your own dog. Annoy your grandma (if she isn't dead yet). Annoy yourself. Annoy other annoying people.

FUTURE RELEASES

- Pretty display interface
- Configure modulator connections
- Additional controls
- Customizable preferences

It looks that there has been some work put into this so I wonder why there was no work in coming up with a name!?

Google Play:
https://play.google.com/store/apps/details?id=com.yossibarel.electrodrum

High-quality 16-channel synth, each channel has extensive effects such as reverb, delay, flanger, filters, and more .... Which includes extensive modular options such as: LFO, ADSR, Sequencer, touch control, and more ...

This is a preview of what is to come and it does look and sound interesting just this little taste...
Next week is what is said in the YouTube message...

Ether synthesizer a very nice instrument for free with no publicity.

Made in Csound...
​
Recommended download to try out as it sounds better than in this video...
https://play.google.com/store/apps/details?id=com.zebproj.etherpad