diff --git a/packages/backend/src/routes/music.ts b/packages/backend/src/routes/music.ts
index c6909b8..c7627c8 100644
--- a/packages/backend/src/routes/music.ts
+++ b/packages/backend/src/routes/music.ts
@@ -208,7 +208,8 @@ router.get('/:id/stream', async (req, res) => {
     
     res.json({
       streamingUrl: presignedUrl,
-      musicFile,
+    musicFile,
+    contentType: musicFile.contentType || undefined,
     });
   } catch (error) {
     console.error('Streaming error:', error);
diff --git a/packages/backend/src/services/backgroundJobService.ts b/packages/backend/src/services/backgroundJobService.ts
index 75190f0..94f6672 100644
--- a/packages/backend/src/services/backgroundJobService.ts
+++ b/packages/backend/src/services/backgroundJobService.ts
@@ -170,6 +170,22 @@ class BackgroundJobService {
       const s3Service = await S3Service.createFromConfig();
       const audioMetadataService = new AudioMetadataService();
       const songMatchingService = new SongMatchingService();
+
+      // Helper to set correct MIME type based on file extension
+      const guessContentType = (fileName: string): string => {
+        const ext = (fileName.split('.').pop() || '').toLowerCase();
+        switch (ext) {
+          case 'mp3': return 'audio/mpeg';
+          case 'wav': return 'audio/wav';
+          case 'flac': return 'audio/flac';
+          case 'm4a': return 'audio/mp4';
+          case 'aac': return 'audio/aac';
+          case 'ogg': return 'audio/ogg';
+          case 'opus': return 'audio/opus';
+          case 'wma': return 'audio/x-ms-wma';
+          default: return 'application/octet-stream';
+        }
+      };
       
       // Phase 1: Quick filename matching
       this.updateProgress(jobId, {
@@ -240,13 +256,13 @@ class BackgroundJobService {
             }
           }
           
-                      if (matchedSong) {
+          if (matchedSong) {
               const basicMetadata = audioMetadataService.extractBasicMetadataFromFilename(filename);
               const musicFile = new MusicFile({
                 originalName: filename,
                 s3Key: s3File.key,
                 s3Url: `${process.env.S3_ENDPOINT}/${process.env.S3_BUCKET_NAME}/${s3File.key}`,
-                contentType: 'audio/mpeg',
+              contentType: guessContentType(filename),
                 size: s3File.size,
                 ...basicMetadata,
                 songId: matchedSong._id,
@@ -323,7 +339,7 @@ class BackgroundJobService {
               originalName: filename,
               s3Key: s3File.key,
               s3Url: `${process.env.S3_ENDPOINT}/${process.env.S3_BUCKET_NAME}/${s3File.key}`,
-              contentType: 'audio/mpeg',
+              contentType: guessContentType(filename),
               size: s3File.size,
               ...metadata,
             });