diff --git a/package-lock.json b/package-lock.json
index 0f2aa056..ddaf82ad 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -10,7 +10,7 @@
       "license": "MIT",
       "dependencies": {
         "moment-of-symmetry": "^0.4.2",
-        "xen-dev-utils": "^0.6.0"
+        "xen-dev-utils": "^0.6.1"
       },
       "bin": {
         "sonic-weave": "bin/sonic-weave.js"
@@ -4444,9 +4444,9 @@
       }
     },
     "node_modules/xen-dev-utils": {
-      "version": "0.6.0",
-      "resolved": "https://registry.npmjs.org/xen-dev-utils/-/xen-dev-utils-0.6.0.tgz",
-      "integrity": "sha512-pBxjTVl6i+eNIkVpRY/mt4fat+4x1jYnAVX+S98rX3sIrJwDO1dcwviFzm8R5a4R3vC49yaQdOP7inkM6Bq4gA==",
+      "version": "0.6.1",
+      "resolved": "https://registry.npmjs.org/xen-dev-utils/-/xen-dev-utils-0.6.1.tgz",
+      "integrity": "sha512-smdLvCIYnAuwGiVdj67kW8kS37gwtUFBF253ukTa4V7BfVglt7HYR9r1EQTCB8FC1J8rdNY++M8TRID+YNsH4A==",
       "engines": {
         "node": ">=10.6.0"
       },
diff --git a/package.json b/package.json
index 34c833a3..8e81ab0b 100644
--- a/package.json
+++ b/package.json
@@ -68,7 +68,7 @@
   },
   "dependencies": {
     "moment-of-symmetry": "^0.4.2",
-    "xen-dev-utils": "^0.6.0"
+    "xen-dev-utils": "^0.6.1"
   },
   "engines": {
     "node": ">=12.0.0"
diff --git a/src/__tests__/interval.spec.ts b/src/__tests__/interval.spec.ts
index ecc6b2fe..3fa0b266 100644
--- a/src/__tests__/interval.spec.ts
+++ b/src/__tests__/interval.spec.ts
@@ -1,7 +1,8 @@
 import {describe, it, expect} from 'vitest';
 import {TimeMonzo} from '../monzo';
-import {intervalValueAs} from '../interval';
+import {Interval, intervalValueAs} from '../interval';
 import {FractionLiteral, NedjiLiteral} from '../expression';
+import {sw} from '../parser';
 
 describe('Idempontent formatting', () => {
   it('has stable ratios (common factor)', () => {
@@ -42,3 +43,72 @@ describe('Idempontent formatting', () => {
     expect(node.denominator).toBe(12);
   });
 });
+
+const SERIALIZED =
+  '["hello",{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":2,"d":1},{"n":1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},"domain":"linear","steps":0,"label":"","node":{"type":"IntegerLiteral","value":"12"},"trackingIds":[]},12,{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":1,"d":1},{"n":1,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},"domain":"linear","steps":0,"label":"","node":{"type":"DecimalLiteral","sign":"","whole":"1","fractional":"2","exponent":null,"flavor":"e"},"trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":0,"d":1},{"n":-1,"d":1},{"n":1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},"domain":"linear","steps":0,"label":"","node":{"type":"FractionLiteral","numerator":"5","denominator":"3"},"trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":1,"d":3},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},"domain":"linear","steps":0,"label":"","node":{"type":"RadicalLiteral","argument":{"n":2,"d":1},"exponent":{"n":1,"d":3}},"trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":46797,"d":80000}],"residual":{"n":1,"d":1}},"domain":"logarithmic","steps":0,"label":"","node":{"type":"CentsLiteral","sign":"","whole":"701","fractional":"955","exponent":null,"real":false},"trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-4,"d":1},{"n":4,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},"domain":"logarithmic","steps":0,"label":"","node":{"type":"SquareSuperparticular","start":"9","end":null},"trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[],"residual":{"n":1,"d":1}},"domain":"logarithmic","steps":3,"label":"","node":{"type":"StepLiteral","count":3},"trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":0,"d":1},{"n":6,"d":13},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},"domain":"logarithmic","steps":0,"label":"","node":{"type":"NedjiLiteral","numerator":6,"denominator":13,"equaveNumerator":3,"equaveDenominator":null},"trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-2,"d":1},{"n":0,"d":1},{"n":1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},"domain":"logarithmic","steps":0,"label":"","node":{"ups":0,"lifts":0,"type":"FJS","pythagorean":{"type":"Pythagorean","quality":{"fraction":"","quality":"M"},"degree":{"negative":false,"base":3,"octaves":0,"imperfect":true}},"superscripts":[[5,""]],"subscripts":[]},"trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":1,"d":1},{"n":-2,"d":1},{"n":0,"d":1},{"n":1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},"domain":"logarithmic","steps":0,"label":"","node":{"ups":0,"lifts":0,"type":"AbsoluteFJS","pitch":{"type":"AbsolutePitch","nominal":"A","accidentals":[{"fraction":"","accidental":"b"}],"octave":4},"superscripts":[[7,""]],"subscripts":[]},"trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":-1,"d":1},"primeExponents":[{"n":0,"d":1},{"n":1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":37,"d":1}},"domain":"linear","steps":0,"label":"","trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":1,"d":1},"primeExponents":[{"n":-3,"d":1},{"n":1,"d":1},{"n":-3,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},"domain":"linear","steps":0,"label":"","trackingIds":[]},{"type":"Interval","value":{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-3,"d":1},{"n":1,"d":1},{"n":1,"d":1}],"residual":{"n":1,"d":1}},"domain":"logarithmic","steps":0,"label":"","node":{"ups":0,"lifts":0,"type":"MonzoLiteral","components":[{"sign":"-","left":3,"separator":"","right":"","exponent":null},{"sign":"","left":1,"separator":"","right":"","exponent":null},{"sign":"","left":1,"separator":"","right":"","exponent":null}],"basis":[]},"trackingIds":[]}]';
+
+describe('Interval JSON serialization', () => {
+  it('can be serialized alongside other data', () => {
+    const data: any = [
+      'hello',
+      sw`12`,
+      12,
+      sw`1.2e`,
+      sw`5/3`,
+      sw`radical(2 /^ 3)`,
+      sw`701.955`,
+      sw`S9`,
+      sw`3°`,
+      sw`6\\13<3>`,
+      sw`M3^5`,
+      sw`Ab4^7`,
+      sw`111 Hz`,
+      sw`3ms`,
+      sw`[-3 1 1>`,
+    ];
+    const serialized = JSON.stringify(data);
+    expect(serialized).toBe(SERIALIZED);
+  });
+
+  it('can be deserialized alongside other data', () => {
+    const data = JSON.parse(SERIALIZED, Interval.reviver);
+    expect(data).toHaveLength(15);
+    expect(data[0]).toBe('hello');
+    expect(data[2]).toBe(12);
+    expect(data.map(datum => datum.toString())).toEqual([
+      'hello',
+      '12',
+      '12',
+      '1.2e',
+      '5/3',
+      '2^1/3',
+      '701.955',
+      'S9',
+      '3°',
+      '6\\13<3>',
+      'M3^5',
+      'Ab4^7',
+      '111 Hz',
+      '2^-3*3*5^-3*(1s)^1',
+      '[-3 1 1>',
+    ]);
+
+    expect(data.map(datum => datum.valueOf())).toEqual([
+      'hello',
+      12,
+      12,
+      1.2,
+      1.666666666666667,
+      1.2599210498948732,
+      1.499999999250199,
+      1.0124999999999997,
+      1,
+      1.6603888560010867,
+      1.25,
+      1.5555555555555558,
+      111,
+      0.003,
+      1.875,
+    ]);
+  });
+});
diff --git a/src/__tests__/monzo.spec.ts b/src/__tests__/monzo.spec.ts
index ba232f66..7a05f2cb 100644
--- a/src/__tests__/monzo.spec.ts
+++ b/src/__tests__/monzo.spec.ts
@@ -460,16 +460,17 @@ describe('JSON serialization', () => {
       new TimeReal(-1, 777),
       3.5,
       TimeMonzo.fromFraction('81/80'),
+      null,
     ];
     const serialized = JSON.stringify(data);
     expect(serialized).toBe(
-      '["Hello, world!",{"n":10,"d":7},{"type":"TimeReal","timeExponent":-1,"value":777},3.5,{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-4,"d":1},{"n":4,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}}]'
+      '["Hello, world!",{"n":10,"d":7},{"type":"TimeReal","timeExponent":-1,"value":777},3.5,{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-4,"d":1},{"n":4,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},null]'
     );
   });
 
   it('can deserialize an array of primitives, fractions and monzos', () => {
     const serialized =
-      '["Hello, world!",{"n":10,"d":7},{"type":"TimeReal","timeExponent":-1,"value":777},3.5,{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-4,"d":1},{"n":4,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}}]';
+      '["Hello, world!",{"n":10,"d":7},{"type":"TimeReal","timeExponent":-1,"value":777},3.5,{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-4,"d":1},{"n":4,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},null]';
     function reviver(key: string, value: any) {
       return TimeMonzo.reviver(
         key,
@@ -477,7 +478,7 @@ describe('JSON serialization', () => {
       );
     }
     const data = JSON.parse(serialized, reviver);
-    expect(data).toHaveLength(5);
+    expect(data).toHaveLength(6);
 
     expect(data[0]).toBe('Hello, world!');
 
@@ -492,5 +493,7 @@ describe('JSON serialization', () => {
 
     expect(data[4]).toBeInstanceOf(TimeMonzo);
     expect(data[4].toFraction().toFraction()).toBe('81/80');
+
+    expect(data[5]).toBeNull();
   });
 });
diff --git a/src/expression.ts b/src/expression.ts
index 9de8cf02..5e3df0c2 100644
--- a/src/expression.ts
+++ b/src/expression.ts
@@ -1046,3 +1046,104 @@ export function integerToVectorComponent(num: number): VectorComponent {
     exponent: null,
   };
 }
+
+export function literalToJSON(literal?: IntervalLiteral) {
+  if (!literal) {
+    return undefined;
+  }
+  const type = literal.type;
+  switch (literal.type) {
+    case 'IntegerLiteral':
+      return {type, value: literal.value.toString()};
+    case 'DecimalLiteral':
+      return {...literal, whole: literal.whole.toString()};
+    case 'FractionLiteral':
+      return {
+        type,
+        numerator: literal.numerator.toString(),
+        denominator: literal.denominator.toString(),
+      };
+    case 'RadicalLiteral':
+      return {
+        type,
+        argument: literal.argument.toJSON(),
+        exponent: literal.exponent.toJSON(),
+      };
+    case 'CentsLiteral':
+      return {
+        ...literal,
+        whole: literal.whole.toString(),
+      };
+    case 'SquareSuperparticular':
+      return {
+        type,
+        start: literal.start.toString(),
+        end: literal.end && literal.end.toString(),
+      };
+    case 'StepLiteral':
+    case 'NedjiLiteral':
+    case 'CentLiteral':
+    case 'ReciprocalCentLiteral':
+    case 'FJS':
+    case 'AspiringFJS':
+    case 'AbsoluteFJS':
+    case 'AspiringAbsoluteFJS':
+    case 'HertzLiteral':
+    case 'SecondLiteral':
+    case 'ReciprocalLogarithmicHertzLiteral':
+    case 'MonzoLiteral':
+    case 'ValLiteral':
+    case 'SparseOffsetVal':
+    case 'WartsLiteral':
+      return literal;
+  }
+}
+
+export function literalFromJSON(object: any): IntervalLiteral | undefined {
+  if (object === undefined) {
+    return undefined;
+  }
+  const type: IntervalLiteral['type'] = object.type;
+  switch (type) {
+    case 'IntegerLiteral':
+      return {type, value: BigInt(object.value)};
+    case 'DecimalLiteral':
+      return {...object, whole: BigInt(object.whole)};
+    case 'FractionLiteral':
+      return {
+        type,
+        numerator: BigInt(object.numerator),
+        denominator: BigInt(object.denominator),
+      };
+    case 'RadicalLiteral':
+      return {
+        type,
+        argument: Fraction.reviver('argument', object.argument),
+        exponent: Fraction.reviver('exponent', object.exponent),
+      };
+    case 'CentsLiteral':
+      return {...object, whole: BigInt(object.whole)};
+    case 'SquareSuperparticular':
+      return {
+        type,
+        start: BigInt(object.start),
+        end: object.end && BigInt(object.end),
+      };
+    case 'StepLiteral':
+    case 'NedjiLiteral':
+    case 'CentLiteral':
+    case 'ReciprocalCentLiteral':
+    case 'FJS':
+    case 'AspiringFJS':
+    case 'AbsoluteFJS':
+    case 'AspiringAbsoluteFJS':
+    case 'HertzLiteral':
+    case 'SecondLiteral':
+    case 'ReciprocalLogarithmicHertzLiteral':
+    case 'MonzoLiteral':
+    case 'ValLiteral':
+    case 'SparseOffsetVal':
+    case 'WartsLiteral':
+      return object;
+  }
+}
diff --git a/src/interval.ts b/src/interval.ts
index 626c41a8..03253d5e 100644
--- a/src/interval.ts
+++ b/src/interval.ts
@@ -23,6 +23,8 @@ import {
   inferFJSFlavor,
   integerToVectorComponent,
   MonzoLiteral,
+  literalToJSON,
+  literalFromJSON,
 } from './expression';
 import {TimeMonzo, TimeReal} from './monzo';
 import {asAbsoluteFJS, asFJS} from './fjs';
@@ -217,6 +219,61 @@ export class Interval {
     return new Interval(real, 'linear', 0, real.asDecimalLiteral(), convert);
   }
 
+  /**
+   * Revive an {@link Interval} instance produced by `Interval.toJSON()`. Return everything else as is.
+   *
+   * Intended usage:
+   * ```ts
+   * const data = JSON.parse(serializedData, Interval.reviver);
+   * ```
+   *
+   * @param key Property name.
+   * @param value Property value.
+   * @returns Deserialized {@link Interval} instance or other data without modifications.
+   */
+  static reviver(key: string, value: any) {
+    if (
+      typeof value === 'object' &&
+      value !== null &&
+      value.type === 'Interval'
+    ) {
+      let monzo: TimeMonzo | TimeReal;
+      if (value.value.type === 'TimeMonzo') {
+        monzo = TimeMonzo.reviver('value', value.value);
+      } else {
+        monzo = TimeReal.reviver('value', value.value);
+      }
+      const result = new Interval(
+        monzo,
+        value.domain,
+        value.steps,
+        literalFromJSON(value.node)
+      );
+      result.label = value.label;
+      result.color = value.color && new Color(value.color);
+      result.trackingIds = new Set(value.trackingIds);
+      return result;
+    }
+    return value;
+  }
+
+  /**
+   * Serialize the time monzo to a JSON compatible object.
+   * @returns The serialized object with property `type` set to `'TimeMonzo'`.
+   */
+  toJSON() {
+    return {
+      type: 'Interval',
+      value: this.value.toJSON(),
+      domain: this.domain,
+      steps: this.steps,
+      label: this.label,
+      color: this.color && this.color.value,
+      node: literalToJSON(this.node),
+      trackingIds: Array.from(this.trackingIds),
+    };
+  }
+
   /**
    * Clone this {@link Interval} instance without deeply copying any of the parts.
    * @returns An interval like this one but replacing any of the parts won't change the original.
diff --git a/src/monzo.ts b/src/monzo.ts
index 62aa1112..2e7154d6 100644
--- a/src/monzo.ts
+++ b/src/monzo.ts
@@ -222,7 +222,11 @@ export class TimeReal {
    * @returns Deserialized {@link TimeReal} instance or other data without modifications.
    */
   static reviver(key: string, value: any) {
-    if (typeof value === 'object' && value.type === 'TimeReal') {
+    if (
+      typeof value === 'object' &&
+      value !== null &&
+      value.type === 'TimeReal'
+    ) {
       return new TimeReal(value.timeExponent, value.value);
     }
     return value;
@@ -1153,7 +1157,11 @@ export class TimeMonzo {
    * @returns Deserialized {@link TimeMonzo} instance or other data without modifications.
    */
   static reviver(key: string, value: any) {
-    if (typeof value === 'object' && value.type === 'TimeMonzo') {
+    if (
+      typeof value === 'object' &&
+      value !== null &&
+      value.type === 'TimeMonzo'
+    ) {
       const timeExponent = Fraction.reviver('timeExponent', value.timeExponent);
       const primeExponents = (value.primeExponents as UnsignedFraction[]).map(
         (component, i) => Fraction.reviver(i.toString(), component)