Berlin Ethereum meetup March 2016 recap

I went to the Berlin meetup yesterday and even though I missed the talk by Afri Schoedon about the Ethereum Stackexchange, it was really worthwhile. The second talk was by a represantative of Nexus Development about their tool Dapple which is designed to help build contract networks comprised of many interacting contracts. In particular it is a package mangager and deployment tool for Solidity contracts.

In the last segment of the evening ethereum C++ team lead Christian Reitwiessner was answering questions about the Solidity contract language. For this purpose he showcased the online tool Browser Solidity, which simulates an ethereum blockchain. It is well suited to test out contracts and provides an easy to use interface to interact with contracts.

He explained the Solidity contract language using the royalty contract for Tiny Human, which I have taken an interest in lately, as an example. In the next paragraphs  follow my notes regarding this part of the talk.

The general layout of this contract is as follows: It starts with the definition of several Structs. Structs are custom groups of variables. Here is an example from the contract code. Owner is a structure that has two variables, the address and the name of a person that owns a share in this song (i.e. one of the creators).

struct Owner {
address addr; // Can be linked off-chain to a persona (like "Imogen Heap" or "Guitar Guy Bob")
bytes32 name;

After the structs come state variables, that are permanently stored in contract storage. An example is the price of the download.

uint public constant USDDOWNLOADPRICE = 60; //0.6 usd.

After this there are two events defined. As I understand it, events are the hooks that allow other applications to interact with the contract. For instance javascript applications can listen for these events and trigger other actions when they occur. I assume that this is the way the Tiny Human web application notices that a payment has occured and starts the download of the mp3.

event purchasedRight(address indexed payee, bytes32 right);

Then on line 72 of the contract begins the constructor. The constructor is only once executed when the contract is submitted to the ethereum blockchain. In it a bunch of properties are setup, which will be used later. This concludes the constructor.

Directly after the constructor starting on line 142 are the definition of two modifiers. These are used to amend functions, in our case to restrict access to certain functions. Here are the lines from the contract code:

modifier isAdmin() {
if (msg.sender == admin) {

After that follow function definitions. First off the purchase-function is public and thus can be called by everyone. Here and in it`s sub-functions is where the meat of the matter is. “purchase” compares the amount of money that was sent in (denoted with msg.value) with the price of the download. If the money is greater or equal the “addTransaction” (line 167) function will be called. Here the contract will iterate over the owners of the song and issue a payment to each of them. See here:

for (uint i = 0; i < ownersCount; i += 1) {
if (shares[owners[i].name][_right] > 0) {
(owners[i].addr).send(msg.value * shares[owners[i].name][_right] / TOTALSHARES);

After this step the “purchasedRight” event is triggered, which makes the download start in the accompaning web-application. The last part of the contract contains administrative functions. You will see that they use the modifer isAdmin() or isOracle() in the function definiton, which make sure that they can only called by persons with the correct private key. These functions are used to set the current exchange rate, etc.

After explaining these features of the contract, Christian Reitwiessner also said, that it is possible to inherit from a contract. So it is possible to create another mp3-download-contract by setting up the contract like so:

contract AnotherSong is TinyHuman {..

This makes it possible to reuse much of the code.

Thanks to the ethereum foundation for setting up these meetups! They are a great opportunity to learn and get in touch with the ETH community.

View the contract code for Imogen Heaps pioneering self-executing royalty contract

In October 2015 British singer Imogen Heap made headlines by publishing her song “Tiny human” with help of the Ethereum blockchain. A new website makes it now very easy to take a peak behind the scenes and see the contract code that governs the royalty contract. The website is called and you can view the contract here.

This excerpt of the code for instance shows how the money from the sale of “Tiny human” mp3s is divided between Imogen Heap and her seven colaborators:

shares[“Imogen Heap”][‘DOWNLOAD’] = 912500; //91.2500
shares[“Stephanie Appelhans”][‘DOWNLOAD’] = 12500; //1.2500
shares[“Diego Romano”][‘DOWNLOAD’] = 12500; //1.2500
shares[“Yasin Gundisch”][‘DOWNLOAD’] = 12500; //1.2500
shares[“Hoang Nguyen”][‘DOWNLOAD’] = 12500; //1.2500
shares[“Simon Minshall”][‘DOWNLOAD’] = 12500; //1.2500
shares[“David Horwich”][‘DOWNLOAD’] = 12500; //1.2500
shares[“Simon Heyworth”][‘DOWNLOAD’] = 12500; //1.2500

The revolutionary thing about this contract is it’s self-executing nature. This means that the payouts to the musicians are automatically and immediately executed in the instant that a download is sold. Ever heard of musicians being ripped off by the evil music industry? Well, if this sort of music publishing would take over, being ripped off would be a thing of the past. If you look closely at the contract details, you will see that the big music companies like Sony, Warner and Universal have no part in it.

The process of buying the mp3 in my opinion could still be improved though. The website Ujo, which hosts the song, asks you to create a wallet on their site for which you then choose a password. In the next step you have to charge your Ujo-wallet with the necessary funds (the ether amount that corresponds to 0.60 USD) and then pay the song from your Ujo-wallet. This was not how I expected this to work and I would prefer to pay directly from my wallet. However we can hope that this might be further improved, if this way of publishing music gains traction.

The Permanent Web for music and other media content

Since the internet has emerged accessability of music and other media content has vastly improved. iTunes, amazon and simliar vendors offer millions of songs, books and movies instantly for relatively cheap prices. Sites like these pretty much guarantee that artistic and cultural content produced in our day and age will remain easily available and conserved for the future. However what about digital content that is not easily marketable and therefore not available on the big commercial platforms?

For instance what about free songs by lesser known bands, self-published mixtapes by no-name djs, live recordings from concerts or particular radio shows? Content like this might appear on some website, online forum or file-sharing site and then might be soon lost for various reasons. Maybe the creator of the content removes his account, maybe the website ceases to exist or a simple change in the url renders the old links to the content in question invalid.

I ran into this kind of problem a lot, especially after that one time I lost a bunch of mp3s due to my own stupidity and a lack of proper backups. My attempts to get a hold of particular dj-mixes I once possessed often ended in a 404.

A new piece of technology called the Interplanetary File System or IPFS tries to solve this problem and deliver the vision of a Permanent Web. The permanence is achieved, because every user that has a particular file in its IPFS-directory is sharing it with all other users (similar to bittorrent). Therefore as long as only one user has a file, the file is available to everybody.

Another advantage is that this design doesn’t have a central server as bandwidth bottleneck. The decentralized nature allows for potentially much higher download speeds. Over bittorrent the IPFS has the advantage that files are versioned similar to files in a GIT repository. This should make it easy to get new improved versions of a particular content.

The creators have set their aims high: “IPFS is becoming a new major subsystem of the internet. If built right, it could complement or replace HTTP. It could complement or replace even more. It sounds crazy. It is crazy.” (quoted from project description on github)

I am really looking forward to this distributed vision of the internet, among other reasons because it might help me rediscover lost recordings of obscure dj-sets.

Liondub – On Dis Ting Muzik presents two new vinyl releases

Liondub – On Dis Ting is a new label set up by Erik Liondub and veteran MC Navigator. The label just released two EPs that we ( will distribute in cooperation with


The first single is called Sound The Alarm. The hook was contributed by JA-born singer Skarra Mucci and verses are from label boss Navigator. Production comes from the German producer Bassface Sasha and is based around the classic reggae riddim Hot Milk. The tune gets lots of support in the Jungle circuit by djs like Bryan G and others. Reggae heads will be pleased to hear the Sticky Joe reggae version of this tune.

Hot on the heels of this single comes the Junglist Sound EP with four original tunes on one 12″. You get a lot of bang for your buck with this release, because each and every tune of the four is a killer! Navigator teams up with singers like Ranking Joe, David Boomah and Jah Lingua and Bass Nacho to deliver the vocals and the beats are from top producers like Liondub, Aries, Potential Badboy and Marcus Visionary. This is an essential pick!

Louis CK content available for bitcoin

The comedian Louis CK is one of the first content creators to utilize digital currencies in his online shop. For me personally this is actually a big deal, because he is my favourite comedian and I used to buy at his online shop prior to him adding bitcoin as a payment option. Now the bitcoin implementation makes purchasing his downloadable audio and video shows even easier.

The actor / comedian is known for trying out new and experimental distribution strategies for the content he produces. In December 2011 he decided to self-produce a one-hour comedy special and distribute it exclusively on his website .

The move was very successfull. The Rolling Stone reported that downloads exceeded the 1 million dollar mark. In an act of “cutting out the middle-man” he removed distribution companies from the interaction with his fanbase. That is why he might have taken a liking to bitcoin, because the digital currency might enable him to do the same with the payment processors. For the moment though, he chose to use the service of Bitpay to process his bitcoin payments.

There is room for improvement though. The website still requires users to provide an email-address before they can purchase his content. This somewhat diminishes the main benefits of bitcoin payments in purchases of digital content. These are increased protection of data privacy and a better user experience by eliminating the need to divulge any personal data. However it is a good start!

Edit March 2016: There is a new show called “Horace And Pete” available now, with new episodes weekly.

Vinyl Release: Freestylers – Rude Bwoy

The Freestylers have always been on of my favourite acts in electronic music. I got to know their songs as a teenager and they always represented the london breakbeat sound for me with a healthy dose of UK dancehall. Their first album “We Rock Hard” was released in 1998 and included a number of great tracks like “B-Boy Stance” and “Ruffneck”, that were career-defining for the featured MCs Tenor Fly and Navigator.

Over the years the producer duo from London always stayed relevant. Some highlights of their carreer were 2001’s “Get Down Massive”, the seminal single “Tarantula / Fasten Your Seatbelt” featuring Pendulum and the rather underrated track “The Coming Storm” featuring Takura.

In 2015 they are back with “Rude Bwoy”, a track featuring the Jamaican dancehall duo RDX and it comes on Krafty Kut`s imprint Instant Vibes.

I am really honored that our humble vinyl distribution “Propellah” can distribute this vinyl 12-inch. Even more so since the remix on the B-side is by one of my other longtime musical heros Dj Aphrodite. It is actually the perfect match because both artists had a defining influence on the sound of their respective musical genres in the mid to late nineties. While the Freestylers were pushing the Big Beat / Breakbeat sound, Aphrodite`s basslines where dominating the Jump Up Drum n Bass of that time. Finally those two artists can be heard in a huge collaboration.

Have a listen to Freestylers banging 2015 mixtape:

Get this 3-track EP at buyreggae: Freestylers Rude Bwoy vinyl EP

Or find another seller on discogs: Freestylers Rude Bwoy on Discogs

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