diff --git a/Makefile b/Makefile
index 0273ff3..646a4ff 100644
--- a/Makefile
+++ b/Makefile
@@ -6,6 +6,7 @@ Obj=                    \
 		context.o           \
 		environment.o       \
 		errors.o            \
+		format.o            \
 		interpreter.o       \
 		lexer.o             \
 		lines.o             \
diff --git a/include/musique.hh b/include/musique.hh
index 9aa1ac8..97499f8 100644
--- a/include/musique.hh
+++ b/include/musique.hh
@@ -6,9 +6,9 @@
 #include <cstdint>
 #include <cstring>
 #include <functional>
+#include <iostream>
 #include <memory>
 #include <optional>
-#include <ostream>
 #include <span>
 #include <string_view>
 #include <variant>
@@ -784,7 +784,7 @@ struct Block
 	Result<Value> operator()(Interpreter &i, std::vector<Value> params);
 
 	/// Indexing block
-	Result<Value> index(Interpreter &i, unsigned position);
+	Result<Value> index(Interpreter &i, unsigned position) const;
 
 	/// Count of elements in block
 	usize size() const;
@@ -845,7 +845,7 @@ struct Array
 	std::vector<Value> elements;
 
 	/// Index element of an array
-	Result<Value> index(Interpreter &i, unsigned position);
+	Result<Value> index(Interpreter &i, unsigned position) const;
 
 	/// Count of elements
 	usize size() const;
@@ -923,7 +923,7 @@ struct Value
 	Result<Value> operator()(Interpreter &i, std::vector<Value> args);
 
 	/// Index contained value if it can be called
-	Result<Value> index(Interpreter &i, unsigned position);
+	Result<Value> index(Interpreter &i, unsigned position) const;
 
 	/// Return elements count of contained value if it can be measured
 	usize size() const;
@@ -1137,4 +1137,22 @@ template<> struct std::hash<Ast>    { std::size_t operator()(Ast    const&) cons
 template<> struct std::hash<Number> { std::size_t operator()(Number const&) const; };
 template<> struct std::hash<Value>  { std::size_t operator()(Value  const&) const; };
 
+struct Value_Formatter
+{
+	enum Context
+	{
+		Free,
+		Inside_Block
+	};
+
+	Context context = Free;
+	unsigned indent = 0;
+
+	Value_Formatter nest(Context nested = Free) const;
+
+	Result<void> format(std::ostream& os, Interpreter &interpreter, Value const& value);
+};
+
+Result<std::string> format(Interpreter &i, Value const& value);
+
 #endif
diff --git a/src/format.cc b/src/format.cc
new file mode 100644
index 0000000..4af2118
--- /dev/null
+++ b/src/format.cc
@@ -0,0 +1,70 @@
+#include <musique.hh>
+#include <sstream>
+
+Result<std::string> format(Interpreter &i, Value const& value)
+{
+	std::stringstream ss;
+	Try(Value_Formatter{}.format(ss, i, value));
+	return ss.str();
+}
+
+Value_Formatter Value_Formatter::nest(Context nested) const
+{
+	return Value_Formatter { .context = nested, .indent = indent + 2 };
+}
+
+std::optional<Error> Value_Formatter::format(std::ostream& os, Interpreter &interpreter, Value const& value)
+{
+	switch (value.type) {
+	break; case Value::Type::Nil:
+		os << "nil";
+
+	break; case Value::Type::Symbol:
+		os << value.s;
+
+	break; case Value::Type::Bool:
+		os << std::boolalpha << value.b;
+
+	break; case Value::Type::Number:
+		if (auto n = value.n.simplify(); n.den == 1) {
+			os << n.num << '/' << n.den;
+		} else {
+			os << n.num;
+		}
+
+	break; case Value::Type::Intrinsic:
+		for (auto const& [key, val] : Env::global->variables) {
+			if (val.type == Value::Type::Intrinsic && val.intr == value.intr) {
+				os << "<intrinsic '" << key << "'>";
+				return {};
+			}
+		}
+		os << "<intrinsic>";
+
+
+	break; case Value::Type::Array:
+		os << '[';
+		for (auto i = 0u; i < value.array.elements.size(); ++i) {
+			if (i > 0) {
+				os << "; ";
+			}
+			Try(nest(Inside_Block).format(os, interpreter, value.array.elements[i]));
+		}
+		os << ']';
+
+	break; case Value::Type::Block:
+		os << '[';
+		for (auto i = 0u; i < value.blk.size(); ++i) {
+			if (i > 0) {
+				os << "; ";
+			}
+			Try(nest(Inside_Block).format(os, interpreter, Try(value.index(interpreter, i))));
+		}
+		os << ']';
+
+	break; case Value::Type::Music:
+		os << value.chord;
+	}
+
+	return {};
+}
diff --git a/src/main.cc b/src/main.cc
index 9b3409c..0fdb772 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -126,9 +126,9 @@ struct Runner
 			midi_input_event_loop.detach();
 		}
 
-		Env::global->force_define("say", +[](Interpreter&, std::vector<Value> args) -> Result<Value> {
+		Env::global->force_define("say", +[](Interpreter &interpreter, std::vector<Value> args) -> Result<Value> {
 			for (auto it = args.begin(); it != args.end(); ++it) {
-			std::cout << *it;
+				Try(format(interpreter, *it));
 				if (std::next(it) != args.end())
 					std::cout << ' ';
 			}
@@ -162,7 +162,7 @@ struct Runner
 			return {};
 		}
 		if (auto result = Try(interpreter.eval(std::move(ast))); output && result.type != Value::Type::Nil) {
-			std::cout << result << std::endl;
+			std::cout << Try(format(interpreter, result)) << std::endl;
 		}
 		return {};
 	}
diff --git a/src/value.cc b/src/value.cc
index 2923903..57477bc 100644
--- a/src/value.cc
+++ b/src/value.cc
@@ -169,7 +169,7 @@ Result<Value> Value::operator()(Interpreter &i, std::vector<Value> args)
 	}
 }
 
-Result<Value> Value::index(Interpreter &i, unsigned position)
+Result<Value> Value::index(Interpreter &i, unsigned position) const
 {
 	switch (type) {
 	case Type::Block:
@@ -361,7 +361,7 @@ static inline Result<void> guard_index(unsigned index, unsigned size)
 }
 
 // TODO Add memoization
-Result<Value> Block::index(Interpreter &i, unsigned position)
+Result<Value> Block::index(Interpreter &i, unsigned position) const
 {
 	assert(parameters.size() == 0, "cannot index into block with parameters (for now)");
 	if (body.type != Ast::Type::Sequence) {
@@ -378,7 +378,7 @@ usize Block::size() const
 	return body.type == Ast::Type::Sequence ? body.arguments.size() : 1;
 }
 
-Result<Value> Array::index(Interpreter &, unsigned position)
+Result<Value> Array::index(Interpreter &, unsigned position) const
 {
 	Try(guard_index(position, elements.size()));
 	return elements[position];