diff --git a/packages/tourmaline/src/lib/client/load-profile.ts b/packages/tourmaline/src/lib/client/load-profile.ts
index 81453b3..9747012 100644
--- a/packages/tourmaline/src/lib/client/load-profile.ts
+++ b/packages/tourmaline/src/lib/client/load-profile.ts
@@ -159,6 +159,9 @@ export function computeProfile(
     albumMilestones: data.albumMilestones,
     longestNotListenedGap: data.longestNotListenedGap,
     recommendations: buildRecommendations(data.topArtists, data.allArtists, artistInfos),
+    monthlyArtistPlays: [...data.monthlyArtistPlays.entries()]
+      .sort(([a], [b]) => a.localeCompare(b))
+      .map(([month, plays]) => [month, [...plays.entries()]]),
   };
 
   const sessions = deriveSessions(filtered);
diff --git a/packages/tourmaline/src/lib/types.ts b/packages/tourmaline/src/lib/types.ts
index dd4cf32..90d7c46 100644
--- a/packages/tourmaline/src/lib/types.ts
+++ b/packages/tourmaline/src/lib/types.ts
@@ -137,6 +137,12 @@ export interface ListenerProfile {
   albumMilestones: Milestone[];
   longestNotListenedGap: Gap | null;
   recommendations: Recommendation[];
+  /**
+   * Chronologically ordered per-month artist play counts, serialized as
+   * tuples (Maps don't survive structured cloning the way we need for
+   * $state). Used by the bar-chart-race visualization.
+   */
+  monthlyArtistPlays: Array<[month: string, plays: Array<[artist: string, count: number]>]>;
 }
 
 export interface UnusualMonth {