Okay so it is not Android but it is a portable and old school and funky, so felt that it had to get mentioned. Plus that an old gameboy can be had for like 10-15 moneys...
Ahh the cartridge is more expensive of course but analogue mojo with three channels for 69 moneys is more or less what other gadgets cost, like pocket operators and the like... Plus have admiration for this single developer to just keep pushing such a niche product as much as he is.
Here are some facts and link:
r = Rectangular Wave
- Dual oscillators
Variable pulse width
Low-pass filter with adjustable resonance
- Single impulses
Extra-resonant bandpass filter for 808-like drum sounds.
- True analog noise generator or
Dual square waves
Bandpass filter with medium resonance
On the original Game Boy models, one pin of the cartridge connector functions as audio input, connected to the built-in amplifier. This unique feature allows to generate sound on the cart and play it through the headphone output on a completely analog signal path.
In the nanoloop mono cart, the analog components (op-amps, comparators, logic cells etc) of a PIC microcontroller are connected and configured in such a way that they form a hybrid soundchip with 3 analog filters and a true random noise generstor, using only a few passive external components.
The cart is a flat but very robust PCB with all electronic parts embedded.
Nanoloop mono is a stepsequencer with per-step control for all parameters. There are 8 banks of flash memory each of which can hold 15 patterns per channel and a song structure.
DMG (original Game Boy) OK, clean and bassy
Game Boy Pocketworks, but less bass, more hiss, whine
Game Boy Colorworks, but very little / distorted bass, a lot of hum and whine
Game Boy Advancedoesn't work, cart won't even boot
Allthough amplitudes are the same as with internal sound, with nanoloop mono's softer characterisic, differences in audio quality are more noticeable.
Some improvement is possible by adding capacitors to the Game Boy's main board ("bass mod" and "noise filter mod"). However, GB Pocket will still produce a high-pitched whine and GB color will still hum and distort basses.
In conclusion, only the original Dot Matrix Game Boy can be recommended.
Nanoloop mono offers the same sync options as nanoloop one.