diff --git a/veza-backend-api/internal/core/marketplace/service.go b/veza-backend-api/internal/core/marketplace/service.go
index f549699dc..db8fbeed7 100644
--- a/veza-backend-api/internal/core/marketplace/service.go
+++ b/veza-backend-api/internal/core/marketplace/service.go
@@ -153,10 +153,12 @@ func (s *Service) CreateProduct(ctx context.Context, product *Product) error {
 	})
 }
 
-// GetProduct retrieves a product by ID
+// GetProduct retrieves a product by ID with preloaded previews and images (v0.401 M1)
 func (s *Service) GetProduct(ctx context.Context, id uuid.UUID) (*Product, error) {
 	var product Product
-	if err := s.db.First(&product, "id = ?", id).Error; err != nil {
+	if err := s.db.Preload("Previews").Preload("Images", func(db *gorm.DB) *gorm.DB {
+		return db.Order("product_images.sort_order ASC")
+	}).First(&product, "id = ?", id).Error; err != nil {
 		if errors.Is(err, gorm.ErrRecordNotFound) {
 			return nil, ErrProductNotFound
 		}
@@ -257,6 +259,22 @@ func (s *Service) ListProducts(ctx context.Context, filters map[string]interface
 		query = query.Where("price <= ?", maxPrice)
 	}
 
+	// v0.401 M1: Filter by BPM, Musical Key, Category
+	if bpm, ok := filters["bpm"]; ok && bpm != nil {
+		switch v := bpm.(type) {
+		case int:
+			query = query.Where("bpm = ?", v)
+		case float64:
+			query = query.Where("bpm = ?", int(v))
+		}
+	}
+	if musicalKey, ok := filters["musical_key"]; ok && musicalKey != "" {
+		query = query.Where("musical_key = ?", musicalKey)
+	}
+	if category, ok := filters["category"]; ok && category != "" {
+		query = query.Where("category = ?", category)
+	}
+
 	// Pagination
 	limit := 20
 	if l, ok := filters["limit"].(int); ok && l > 0 {
diff --git a/veza-backend-api/internal/handlers/marketplace.go b/veza-backend-api/internal/handlers/marketplace.go
index 8853c6dcb..fa0a21069 100644
--- a/veza-backend-api/internal/handlers/marketplace.go
+++ b/veza-backend-api/internal/handlers/marketplace.go
@@ -352,6 +352,17 @@ func (h *MarketplaceHandler) ListProducts(c *gin.Context) {
 	if pType := c.Query("type"); pType != "" {
 		filters["product_type"] = pType
 	}
+	if bpmStr := c.Query("bpm"); bpmStr != "" {
+		if val, err := strconv.Atoi(bpmStr); err == nil && val > 0 {
+			filters["bpm"] = val
+		}
+	}
+	if musicalKey := c.Query("musical_key"); musicalKey != "" {
+		filters["musical_key"] = musicalKey
+	}
+	if category := c.Query("category"); category != "" {
+		filters["category"] = category
+	}
 
 	if minPriceStr := c.Query("min_price"); minPriceStr != "" {
 		if val, err := strconv.ParseFloat(minPriceStr, 64); err == nil {