diff --git a/exp/audio/vorbis/stream.go b/exp/audio/vorbis/stream.go
index bd381fb1c..00c0ff0d3 100644
--- a/exp/audio/vorbis/stream.go
+++ b/exp/audio/vorbis/stream.go
@@ -16,29 +16,23 @@ package vorbis
 
 import (
 	"bytes"
-	"io"
 	"time"
 )
 
-type Stream interface {
-	io.ReadSeeker
-	Len() time.Duration
-}
-
-type stream struct {
+type Stream struct {
 	buf        *bytes.Reader
 	sampleRate int
 }
 
-func (s *stream) Read(p []byte) (int, error) {
+func (s *Stream) Read(p []byte) (int, error) {
 	return s.buf.Read(p)
 }
 
-func (s *stream) Seek(offset int64, whence int) (int64, error) {
+func (s *Stream) Seek(offset int64, whence int) (int64, error) {
 	return s.buf.Seek(offset, whence)
 }
 
-func (s *stream) Len() time.Duration {
+func (s *Stream) Len() time.Duration {
 	const bytesPerSample = 4
 	return time.Duration(s.buf.Len()/bytesPerSample) * time.Second / time.Duration(s.sampleRate)
 }
diff --git a/exp/audio/vorbis/vorbis.go b/exp/audio/vorbis/vorbis.go
index b83ef77cf..57e36fc57 100644
--- a/exp/audio/vorbis/vorbis.go
+++ b/exp/audio/vorbis/vorbis.go
@@ -27,7 +27,7 @@ import (
 	"github.com/hajimehoshi/go-vorbis"
 )
 
-func Decode(context *audio.Context, src io.Reader) (Stream, error) {
+func Decode(context *audio.Context, src io.Reader) (*Stream, error) {
 	decoded, channels, sampleRate, err := vorbis.Decode(src)
 	if err != nil {
 		return nil, err
@@ -44,7 +44,7 @@ func Decode(context *audio.Context, src io.Reader) (Stream, error) {
 	if err != nil {
 		return nil, err
 	}
-	s := &stream{
+	s := &Stream{
 		buf:        bytes.NewReader(b),
 		sampleRate: sampleRate,
 	}
diff --git a/exp/audio/vorbis/vorbis_js.go b/exp/audio/vorbis/vorbis_js.go
index ae8259b57..58131bfea 100644
--- a/exp/audio/vorbis/vorbis_js.go
+++ b/exp/audio/vorbis/vorbis_js.go
@@ -29,12 +29,12 @@ import (
 // TODO: This just uses decodeAudioData can treat audio files other than Ogg/Vorbis.
 // TODO: This doesn't work on iOS which doesn't have Ogg/Vorbis decoder.
 
-func Decode(context *audio.Context, src io.Reader) (Stream, error) {
+func Decode(context *audio.Context, src io.Reader) (*Stream, error) {
 	b, err := ioutil.ReadAll(src)
 	if err != nil {
 		return nil, err
 	}
-	s := &stream{
+	s := &Stream{
 		sampleRate: context.SampleRate(),
 	}
 	ch := make(chan struct{})