Starting a REPL

Once you've made it through the process of Installing Overtone you'll want to start a REPL so that you can start giving it music-making instructions.

For those not aware of the term REPL, it stands for Read Evaluate Print Loop and dates back to the early days of Lisps. Other languages call it the console or an interactive session or a prompt. Essentially it gives you a way to communicate live with Overtone so you can make it do your bidding and control it in real time - at least as fast as you can type!

You'll know when you've entered a REPL session because the terminal prompt will change from something like $ to user=>. You can then enter Clojure forms as text and press return to execute it.

Firing up a REPL

All instructions require you to have the working directory of your terminal set to your project directory (i.e. tutorial). Once you see the => prompt, try typing the Clojure form (+ 1 2) and press return to evaluate and return the answer 3. This is the REPL in full action:

• READ - Clojure reads the form (+ 1 2) as text
• EVALUATE - Clojure does the sum 1 + 2 and resolves it to 3
• PRINT - Clojure then prints the answer out to the screen
• LOOP - Clojure writes the prompt user=> again and patiently waits for another command to read.

Later on we'll use this exact process to make music rather than doing basic sums...

$ clj
=> (+ 1 2)
3
=>

Working directly via a command line REPL like this is not very convenient. What you want instead is to write some code in a file or buffer in your editor, and then run it from there. For this you need a clojure-powered editor that knows how to start or connect to a Clojure REPL. Clojure.org has an overview of the most popular options

What next?

Learn how to Connect scsynth then head over to Getting Started to learn how to make some radical sounds.