diff --git a/include/libremidi/libremidi.cpp b/include/libremidi/libremidi.cpp
index dcce6eb..3cb79ae 100644
--- a/include/libremidi/libremidi.cpp
+++ b/include/libremidi/libremidi.cpp
@@ -59,7 +59,7 @@ libremidi::API midi_api(const std::any& conf)
   libremidi::API ret = libremidi::API::UNSPECIFIED;
   midi_any::for_all_backends([&]<typename T>(T) {
     if (std::any_cast<typename T::midi_in_configuration>(&conf)
-        || std::any_cast<typename T::midi_out_configuration>(&conf)
+        || std::any_cast<typename T::midi_out_configuration>(&conf)
         || std::any_cast<typename T::midi_observer_configuration>(&conf))
     {
       ret = T::API;
diff --git a/include/libremidi/midi_in.cpp b/include/libremidi/midi_in.cpp
index f47606e..f1c854c 100644
--- a/include/libremidi/midi_in.cpp
+++ b/include/libremidi/midi_in.cpp
@@ -228,14 +228,47 @@ make_midi2_in(const ump_input_configuration& base_conf, const std::any& api_conf
   {
     return make_midi2_in(base_conf);
   }
-  else if (auto api = std::any_cast<libremidi::API>(&api_conf))
+  else if (auto api_p = std::any_cast<libremidi::API>(&api_conf))
   {
-    return make_midi_in(base_conf, midi_in_configuration_for(*api), midi2::available_backends);
+    if (*api_p == libremidi::API::UNSPECIFIED)
+    {
+      if (auto backend = make_midi_in(
+              base_conf, midi_in_configuration_for(libremidi::midi2::default_api()),
+              midi2::available_backends))
+        return backend;
+
+      auto c2 = convert_midi2_to_midi1_input_configuration(base_conf);
+      if (auto backend = make_midi_in(
+              c2, midi_in_configuration_for(libremidi::midi1::default_api()),
+              midi1::available_backends))
+        return backend;
+    }
+    else if (is_midi2(*api_p))
+    {
+      // all good
+      return make_midi_in(base_conf, midi_in_configuration_for(*api_p), midi2::available_backends);
+    }
+    else if (is_midi1(*api_p))
+    {
+      auto c2 = convert_midi2_to_midi1_input_configuration(base_conf);
+      return make_midi_in(c2, midi_in_configuration_for(*api_p), midi1::available_backends);
+    }
   }
   else
   {
-    return make_midi_in(base_conf, api_conf, midi2::available_backends);
+    const auto api = libremidi::midi_api(api_conf);
+    if (libremidi::is_midi2(api))
+    {
+      return make_midi_in(base_conf, api_conf, midi2::available_backends);
+    }
+    else if (libremidi::is_midi1(api))
+    {
+      auto c2 = convert_midi2_to_midi1_input_configuration(base_conf);
+      return make_midi_in(c2, api_conf, midi1::available_backends);
+    }
   }
+
+  return std::make_unique<midi_in_dummy>(input_configuration{}, dummy_configuration{});
 }
 
 /// MIDI 2 constructors
diff --git a/include/libremidi/midi_out.cpp b/include/libremidi/midi_out.cpp
index 74dcc74..48329c3 100644
--- a/include/libremidi/midi_out.cpp
+++ b/include/libremidi/midi_out.cpp
@@ -64,9 +64,24 @@ make_midi_out(const output_configuration& base_conf, const std::any& api_conf)
   {
     return make_midi_out(base_conf);
   }
-  else if (auto api = std::any_cast<libremidi::API>(&api_conf))
+  else if (auto api_p = std::any_cast<libremidi::API>(&api_conf))
   {
-    return make_midi_out_impl(base_conf, midi_out_configuration_for(*api));
+    if (*api_p == libremidi::API::UNSPECIFIED)
+    {
+      if (auto backend = make_midi_out_impl(
+              base_conf, midi_out_configuration_for(libremidi::midi1::default_api())))
+        return backend;
+
+      if (auto backend = make_midi_out_impl(
+              base_conf, midi_out_configuration_for(libremidi::midi2::default_api())))
+        return backend;
+
+      return std::make_unique<midi_out_dummy>(output_configuration{}, dummy_configuration{});
+    }
+    else
+    {
+      return make_midi_out_impl(base_conf, midi_out_configuration_for(*api_p));
+    }
   }
   else
   {
diff --git a/include/libremidi/observer.cpp b/include/libremidi/observer.cpp
index 72972f6..f9c66ab 100644
--- a/include/libremidi/observer.cpp
+++ b/include/libremidi/observer.cpp
@@ -53,15 +53,30 @@ LIBREMIDI_INLINE auto make_observer_impl(auto base_conf, std::any api_conf)
   return ptr;
 }
 
-LIBREMIDI_INLINE auto make_observer(auto base_conf, std::any api_conf)
+LIBREMIDI_INLINE std::unique_ptr<observer_api> make_observer(auto base_conf, std::any api_conf)
 {
   if (!api_conf.has_value())
   {
     return make_observer(base_conf);
   }
-  else if (auto api = std::any_cast<libremidi::API>(&api_conf))
+  else if (auto api_p = std::any_cast<libremidi::API>(&api_conf))
   {
-    return make_observer_impl(base_conf, observer_configuration_for(*api));
+    if (*api_p == libremidi::API::UNSPECIFIED)
+    {
+      if (auto backend = make_observer_impl(
+              base_conf, observer_configuration_for(libremidi::midi1::default_api())))
+        return backend;
+
+      if (auto backend = make_observer_impl(
+              base_conf, observer_configuration_for(libremidi::midi2::default_api())))
+        return backend;
+
+      return std::make_unique<observer_dummy>(observer_configuration{}, dummy_configuration{});
+    }
+    else
+    {
+      return make_observer_impl(base_conf, observer_configuration_for(*api_p));
+    }
   }
   else
   {