diff --git a/src/AudioIO.cpp b/src/AudioIO.cpp
index a2ad3705e..5c1ec97e1 100644
--- a/src/AudioIO.cpp
+++ b/src/AudioIO.cpp
@@ -770,7 +770,7 @@ class AudioThread {
 
 // The normal wxThread-derived AudioThread class for all other
 // platforms:
-class AudioThread final : public wxThread {
+class AudioThread /* not final */ : public wxThread {
  public:
    AudioThread():wxThread(wxTHREAD_JOINABLE) {}
    ExitCode Entry() override;
@@ -781,7 +781,7 @@ class AudioThread final : public wxThread {
 #ifdef EXPERIMENTAL_MIDI_OUT
 class MidiThread final : public AudioThread {
  public:
-   virtual ExitCode Entry();
+   ExitCode Entry() override;
 };
 #endif
 
@@ -922,7 +922,7 @@ AudioIO::AudioIO()
               _("There was an error initializing the midi i/o layer.\n");
       errStr += _("You will not be able to play midi.\n\n");
       wxString pmErrStr = LAT1CTOWX(Pm_GetErrorText(pmErr));
-      if (pmErrStr)
+      if (!pmErrStr.empty())
          errStr += _("Error: ") + pmErrStr;
       // XXX: we are in libaudacity, popping up dialogs not allowed!  A
       // long-term solution will probably involve exceptions
@@ -1668,7 +1668,7 @@ int AudioIO::StartStream(WaveTrackArray playbackTracks,
 
    bool successMidi = true;
 
-   if(!mMidiPlaybackTracks.IsEmpty()){
+   if(!mMidiPlaybackTracks.empty()){
       successMidi = StartPortMidiStream();
    }
 
@@ -1979,7 +1979,7 @@ PmTimestamp MidiTime(void *info)
 void AudioIO::PrepareMidiIterator(bool send, double offset)
 {
    int i;
-   int nTracks = mMidiPlaybackTracks.GetCount();
+   int nTracks = mMidiPlaybackTracks.size();
    // instead of initializing with an Alg_seq, we use begin_seq()
    // below to add ALL Alg_seq's.
    mIterator = new Alg_iterator(NULL, false);
@@ -2008,7 +2008,7 @@ void AudioIO::PrepareMidiIterator(bool send, double offset)
 bool AudioIO::StartPortMidiStream()
 {
    int i;
-   int nTracks = mMidiPlaybackTracks.GetCount();
+   int nTracks = mMidiPlaybackTracks.size();
    // Only start MIDI stream if there is an open track
    if (nTracks == 0)
       return false;
@@ -2232,7 +2232,7 @@ void AudioIO::StopStream()
       mIterator->end();
 
       // set in_use flags to false
-      int nTracks = mMidiPlaybackTracks.GetCount();
+      int nTracks = mMidiPlaybackTracks.size();
       for (int i = 0; i < nTracks; i++) {
          NoteTrack *t = mMidiPlaybackTracks[i];
          Alg_seq_ptr seq = t->GetSequence();
@@ -2857,7 +2857,8 @@ MidiThread::ExitCode MidiThread::Entry()
                                  gAudioIO->mMidiPlaySpeed + gAudioIO->mT0;
 
             gAudioIO->mMidiOutputComplete =
-               (!gAudioIO->mPlayLooped && timeAtSpeed >= gAudioIO->mT1 + 0.220);
+               (gAudioIO->mPlayMode == gAudioIO->PLAY_STRAIGHT && // PRL:  what if scrubbing?
+                timeAtSpeed >= gAudioIO->mT1 + 0.220);
             // !gAudioIO->mNextEvent);
          }
       }
@@ -3527,7 +3528,7 @@ void AudioIO::OutputEvent()
    // all notes off on all channels"
    if (mNextEvent == &gAllNotesOff) {
       AllNotesOff();
-      if (mPlayLooped) {
+      if (mPlayMode == gAudioIO->PLAY_LOOPED) {
          // jump back to beginning of loop
          mMidiLoopOffset += (mT1 - mT0);
          PrepareMidiIterator(false, mMidiLoopOffset);
@@ -3667,14 +3668,14 @@ bool AudioIO::SetHasSolo(bool hasSolo)
 void AudioIO::FillMidiBuffers()
 {
    bool hasSolo = false;
-   int numPlaybackTracks = gAudioIO->mPlaybackTracks->GetCount();
+   int numPlaybackTracks = gAudioIO->mPlaybackTracks->size();
    int t;
    for(t = 0; t < numPlaybackTracks; t++ )
-      if( gAudioIO->mPlaybackTracks[t]->GetSolo() ) {
+      if( (*gAudioIO->mPlaybackTracks)[t]->GetSolo() ) {
          hasSolo = true;
          break;
       }
-   int numMidiPlaybackTracks = gAudioIO->mMidiPlaybackTracks.GetCount();
+   int numMidiPlaybackTracks = gAudioIO->mMidiPlaybackTracks.size();
    for(t = 0; t < numMidiPlaybackTracks; t++ )
       if( gAudioIO->mMidiPlaybackTracks[t]->GetSolo() ) {
          hasSolo = true;
@@ -3698,7 +3699,7 @@ void AudioIO::FillMidiBuffers()
          // buffer, the cursor tends to jump back to mT0 early.
          // Therefore, if we are in loop mode, and if mTime < mT0,
          // we must not be at the end of the loop yet.
-         if (mPlayLooped && trackTime < mT0) {
+         if (mPlayMode == gAudioIO->PLAY_LOOPED && trackTime < mT0) {
             trackTime += (mT1 - mT0);
          }
          // mTime is shared with another thread so we stored
@@ -4142,7 +4143,7 @@ int audacityAudioCallback(const void *inputBuffer, void *outputBuffer,
             if( (*gAudioIO->mPlaybackTracks)[t]->GetSolo() )
                numSolo++;
 #ifdef EXPERIMENTAL_MIDI_OUT
-         int numMidiPlaybackTracks = gAudioIO->mMidiPlaybackTracks.GetCount();
+         int numMidiPlaybackTracks = gAudioIO->mMidiPlaybackTracks.size();
          for( t = 0; t < numMidiPlaybackTracks; t++ )
             if( gAudioIO->mMidiPlaybackTracks[t]->GetSolo() )
                numSolo++;
diff --git a/src/AudioIO.h b/src/AudioIO.h
index 1acb6ea34..171139a1d 100644
--- a/src/AudioIO.h
+++ b/src/AudioIO.h
@@ -18,11 +18,18 @@
 #include "Experimental.h"
 
 #ifdef USE_MIDI
+
 #ifdef EXPERIMENTAL_MIDI_OUT
 #include "portmidi.h"
 #include "porttime.h"
 #include "allegro.h"
+
+#include <vector>
+class NoteTrack;
+using NoteTrackArray = std::vector < NoteTrack* >;
+
 #endif // EXPERIMENTAL_MIDI_OUT
+
 #endif // USE_MIDI
 
 #if USE_PORTMIXER
diff --git a/src/MixerBoard.cpp b/src/MixerBoard.cpp
index 4b7de1669..574e733e9 100644
--- a/src/MixerBoard.cpp
+++ b/src/MixerBoard.cpp
@@ -1244,7 +1244,7 @@ wxBitmap* MixerBoard::GetMusicalInstrumentBitmap(const WaveTrack* pLeftTrack)
    // random choice:    return mMusicalInstruments[(int)pLeftTrack % mMusicalInstruments.GetCount()].mBitmap;
 
 #ifdef EXPERIMENTAL_MIDI_OUT
-   const wxString strTrackName(name.MakeLower());
+   const wxString strTrackName(wxString{ name }.MakeLower());
 #else
    const wxString strTrackName(pLeftTrack->GetName().MakeLower());
 #endif
diff --git a/src/Track.cpp b/src/Track.cpp
index ca3104a63..c21347ec5 100644
--- a/src/Track.cpp
+++ b/src/Track.cpp
@@ -1303,7 +1303,7 @@ NoteTrackArray TrackList::GetNoteTrackArray(bool selectionOnly)
    for(const auto &track : *this) {
       if (track->GetKind() == Track::Note &&
          (track->GetSelected() || !selectionOnly)) {
-         noteTrackArray.Add(static_cast<NoteTrack*>(track.get()));
+         noteTrackArray.push_back(static_cast<NoteTrack*>(track.get()));
       }
    }
 
diff --git a/src/Track.h b/src/Track.h
index 1bbf3eac8..3084dd752 100644
--- a/src/Track.h
+++ b/src/Track.h
@@ -36,6 +36,7 @@ class Track;
 class LabelTrack;
 class TimeTrack;
 class WaveTrack;
+class NoteTrack;
 class AudacityProject;
 class ZoomInfo;
 
@@ -60,9 +61,10 @@ public:
 #endif
 };
 
+using NoteTrackArray  = std::vector < NoteTrack* >;
+
 #if defined(USE_MIDI)
 class NoteTrack;
-WX_DEFINE_USER_EXPORTED_ARRAY(NoteTrack*, NoteTrackArray, class AUDACITY_DLL_API);
 #endif
 
 class TrackList;
diff --git a/src/TrackPanel.cpp b/src/TrackPanel.cpp
index f8f802aa4..4db423f2e 100644
--- a/src/TrackPanel.cpp
+++ b/src/TrackPanel.cpp
@@ -5429,7 +5429,7 @@ void TrackPanel::HandleSliders(wxMouseEvent &event, bool pan)
                           UndoPush::CONSOLIDATE);
 #ifdef EXPERIMENTAL_MIDI_OUT
     } else {
-      MakeParentPushState(_("Moved velocity slider"), _("Velocity"), true);
+      MakeParentPushState(_("Moved velocity slider"), _("Velocity"), UndoPush::CONSOLIDATE);
     }
 #endif
       SetCapturedTrack( NULL );
@@ -10000,13 +10000,18 @@ void TrackInfo::DrawVelocitySlider(wxDC *dc, NoteTrack *t, wxRect rect) const
 {
     wxRect gainRect;
     int index = t->GetIndex();
-    EnsureSufficientSliders(index);
+
+    //EnsureSufficientSliders(index);
+
     GetGainRect(rect, gainRect);
     if (gainRect.y + gainRect.height < rect.y + rect.height - 19) {
-       mGains[index]->SetStyle(VEL_SLIDER);
+       auto &gain = mGain; // mGains[index];
+       gain->SetStyle(VEL_SLIDER);
        GainSlider(index)->Move(wxPoint(gainRect.x, gainRect.y));
        GainSlider(index)->Set(t->GetGain());
-       GainSlider(index)->OnPaint(*dc, t->GetSelected());
+       GainSlider(index)->OnPaint(*dc
+          // , t->GetSelected()
+       );
     }
 }
 #endif
diff --git a/src/TrackPanel.h b/src/TrackPanel.h
index d4f13fea5..d097d3c10 100644
--- a/src/TrackPanel.h
+++ b/src/TrackPanel.h
@@ -110,6 +110,10 @@ public:
    LWSlider * GainSlider(WaveTrack *t, bool captured = false) const;
    LWSlider * PanSlider(WaveTrack *t, bool captured = false) const;
 
+#ifdef EXPERIMENTAL_MIDI_OUT
+   LWSlider *GainSlider(int index) const;
+#endif
+
 private:
    TrackPanel * pParent;
    wxFont mFont;
diff --git a/src/prefs/MidiIOPrefs.cpp b/src/prefs/MidiIOPrefs.cpp
index b8a0c816f..926775602 100644
--- a/src/prefs/MidiIOPrefs.cpp
+++ b/src/prefs/MidiIOPrefs.cpp
@@ -120,7 +120,7 @@ void MidiIOPrefs::PopulateOrExchange( ShuttleGui & S ) {
       {
          S.Id(HostID);
          /* i18n-hint: (noun) */
-         mHost = S.TieChoice(_("Host":),
+         mHost = S.TieChoice(_("Host:"),
                              wxT("/MidiIO/Host"),
                              wxT(""),
                              mHostNames,
diff --git a/src/toolbars/ControlToolBar.cpp b/src/toolbars/ControlToolBar.cpp
index ccc8a72dd..662fec926 100644
--- a/src/toolbars/ControlToolBar.cpp
+++ b/src/toolbars/ControlToolBar.cpp
@@ -843,7 +843,7 @@ void ControlToolBar::OnRecord(wxCommandEvent &evt)
       if(duplex){
          playbackTracks = trackList->GetWaveTrackArray(false);
 #ifdef EXPERIMENTAL_MIDI_OUT
-         midiTracks = t->GetNoteTrackArray(false);
+         midiTracks = trackList->GetNoteTrackArray(false);
 #endif
      }
       else {