diff --git a/extras/Projucer/Source/ProjectSaving/jucer_ProjectSaver.cpp b/extras/Projucer/Source/ProjectSaving/jucer_ProjectSaver.cpp
index 4aee5d78f5..cd91adccff 100644
--- a/extras/Projucer/Source/ProjectSaving/jucer_ProjectSaver.cpp
+++ b/extras/Projucer/Source/ProjectSaving/jucer_ProjectSaver.cpp
@@ -41,6 +41,7 @@ namespace
         jassert ((configs.size() & 1) == 0);  // looks like a syntax error in the configs?
 
         int maxVal = 0;
+
         for (int i = (isInput ? 0 : 1); i < configs.size(); i += 2)
             maxVal = jmax (maxVal, configs[i].getIntValue());
 
@@ -59,16 +60,16 @@ namespace
 
     inline String valueToCharLiteral (const var& v)
     {
-        String fourCharCode = v.toString().trim().substring (0, 4);
+        auto fourCharCode = v.toString().trim().substring (0, 4);
         uint32 hexRepresentation = 0;
 
         for (int i = 0; i < 4; ++i)
-            hexRepresentation = (hexRepresentation << 8U)
-                             |  (static_cast<unsigned int> (fourCharCode[i]) & 0xffU);
+            hexRepresentation = (hexRepresentation << 8u)
+                             |  (static_cast<unsigned int> (fourCharCode[i]) & 0xffu);
 
-        return String ("0x") + String::toHexString (static_cast<int> (hexRepresentation))
-                             + String (" // ")
-                             + CppTokeniserFunctions::addEscapeChars (fourCharCode).quoted ('\'');
+        return "0x" + String::toHexString (static_cast<int> (hexRepresentation))
+                 + " // "
+                 + CppTokeniserFunctions::addEscapeChars (fourCharCode).quoted ('\'');
     }
 }
 
diff --git a/modules/juce_audio_formats/codecs/juce_CoreAudioFormat.cpp b/modules/juce_audio_formats/codecs/juce_CoreAudioFormat.cpp
index 990d80a636..e6c4785e7b 100644
--- a/modules/juce_audio_formats/codecs/juce_CoreAudioFormat.cpp
+++ b/modules/juce_audio_formats/codecs/juce_CoreAudioFormat.cpp
@@ -630,7 +630,7 @@ public:
             {
                 auto labels = CoreAudioLayouts::fromCoreAudio (tagEntry.tag);
 
-                expect (! labels.isDiscreteLayout(), String ("Tag \"") + String (tagEntry.name) + "\" is not handled by JUCE");
+                expect (! labels.isDiscreteLayout(), "Tag \"" + String (tagEntry.name) + "\" is not handled by JUCE");
             }
         }
 
@@ -641,7 +641,7 @@ public:
             {
                 auto labels = CoreAudioLayouts::getSpeakerLayoutForCoreAudioTag (tagEntry.tag);
 
-                expect (labels.size() == (tagEntry.tag & 0xffff), String ("Tag \"") + String (tagEntry.name) + "\" has incorrect channel count");
+                expect (labels.size() == (tagEntry.tag & 0xffff), "Tag \"" + String (tagEntry.name) + "\" has incorrect channel count");
             }
         }
 
@@ -655,7 +655,7 @@ public:
 
                 for (int i = 0; i < (labels.size() - 1); ++i)
                     expect (labels.getReference (i) != labels.getReference (i + 1),
-                            String ("Tag \"") + String (tagEntry.name) + "\" has the same speaker twice");
+                            "Tag \"" + String (tagEntry.name) + "\" has the same speaker twice");
             }
         }
 
@@ -665,7 +665,7 @@ public:
             for (auto tagEntry : knownTags)
                 expect (AudioChannelSet::channelSetWithChannels (CoreAudioLayouts::getSpeakerLayoutForCoreAudioTag (tagEntry.tag))
                             == CoreAudioLayouts::fromCoreAudio (tagEntry.tag),
-                        String ("Tag \"") + String (tagEntry.name) + "\" is not converted consistantly by JUCE");
+                        "Tag \"" + String (tagEntry.name) + "\" is not converted consistantly by JUCE");
         }
 
         {
@@ -677,7 +677,7 @@ public:
                     continue;
 
                 expect (CoreAudioLayouts::fromCoreAudio (tagEntry.tag) == tagEntry.equivalentChannelSet,
-                        String ("Documentation for tag \"") + String (tagEntry.name) + "\" is incorrect");
+                        "Documentation for tag \"" + String (tagEntry.name) + "\" is incorrect");
             }
         }
 
@@ -690,7 +690,7 @@ public:
                     continue;
 
                 expect (CoreAudioLayouts::toCoreAudio (tagEntry.equivalentChannelSet) == tagEntry.tag,
-                        String ("Incorrect reverse conversion for tag \"") + String (tagEntry.name) + "\"");
+                        "Incorrect reverse conversion for tag \"" + String (tagEntry.name) + "\"");
             }
         }
     }
diff --git a/modules/juce_audio_processors/processors/juce_AudioProcessor.cpp b/modules/juce_audio_processors/processors/juce_AudioProcessor.cpp
index dd3c594aae..f1e4e0cefd 100644
--- a/modules/juce_audio_processors/processors/juce_AudioProcessor.cpp
+++ b/modules/juce_audio_processors/processors/juce_AudioProcessor.cpp
@@ -293,15 +293,8 @@ void AudioProcessor::getNextBestLayout (const BusesLayout& desiredLayout, BusesL
 
             // try setting all other buses to the identical layout
             BusesLayout allTheSame;
-
-            for (int oDir = 0; oDir < 2; ++oDir)
-            {
-                bool oIsInput = (oDir == 0);
-                auto oBusNum = getBusCount (oIsInput);
-
-                for (int oBusIndex = 0; oBusIndex < oBusNum; ++oBusIndex)
-                    (oIsInput ? allTheSame.inputBuses : allTheSame.outputBuses).add (requested);
-            }
+            allTheSame.inputBuses.insertMultiple (-1, requested, getBusCount (true));
+            allTheSame.outputBuses.insertMultiple (-1, requested, getBusCount (false));
 
             if (checkBusesLayoutSupported (allTheSame))
             {
@@ -327,18 +320,18 @@ void AudioProcessor::getNextBestLayout (const BusesLayout& desiredLayout, BusesL
 }
 
 //==============================================================================
-void AudioProcessor::setPlayHead (AudioPlayHead* const newPlayHead)
+void AudioProcessor::setPlayHead (AudioPlayHead* newPlayHead)
 {
     playHead = newPlayHead;
 }
 
-void AudioProcessor::addListener (AudioProcessorListener* const newListener)
+void AudioProcessor::addListener (AudioProcessorListener* newListener)
 {
     const ScopedLock sl (listenerLock);
     listeners.addIfNotAlreadyThere (newListener);
 }
 
-void AudioProcessor::removeListener (AudioProcessorListener* const listenerToRemove)
+void AudioProcessor::removeListener (AudioProcessorListener* listenerToRemove)
 {
     const ScopedLock sl (listenerLock);
     listeners.removeFirstMatchingValue (listenerToRemove);
@@ -348,7 +341,7 @@ void AudioProcessor::setPlayConfigDetails (int newNumIns, int newNumOuts, double
 {
     bool success = true;
 
-    if (getTotalNumInputChannels()  != newNumIns)
+    if (getTotalNumInputChannels() != newNumIns)
         success &= setChannelLayoutOfBus (true,  0, AudioChannelSet::canonicalChannelSet (newNumIns));
 
     // failed to find a compatible input configuration
@@ -740,10 +733,10 @@ AudioProcessor::BusesProperties AudioProcessor::busesPropertiesFromLayoutArray (
     BusesProperties ioProps;
 
     if (config[0].inChannels > 0)
-        ioProps.addBus (true, String ("Input"), AudioChannelSet::canonicalChannelSet (config[0].inChannels));
+        ioProps.addBus (true, "Input", AudioChannelSet::canonicalChannelSet (config[0].inChannels));
 
     if (config[0].outChannels > 0)
-        ioProps.addBus (false, String ("Output"), AudioChannelSet::canonicalChannelSet (config[0].outChannels));
+        ioProps.addBus (false, "Output", AudioChannelSet::canonicalChannelSet (config[0].outChannels));
 
     return ioProps;
 }
diff --git a/modules/juce_core/native/juce_android_Files.cpp b/modules/juce_core/native/juce_android_Files.cpp
index 98df86c84b..5ef671f982 100644
--- a/modules/juce_core/native/juce_android_Files.cpp
+++ b/modules/juce_core/native/juce_android_Files.cpp
@@ -143,7 +143,7 @@ public:
             if (type == "image")
                 type = "images";
 
-            return getCursorDataColumn (URL (String ("content://media/external/") + type + "/media"),
+            return getCursorDataColumn (URL ("content://media/external/" + type + "/media"),
                                         "_id=?", StringArray {mediaId});
         }
 
diff --git a/modules/juce_core/native/juce_curl_Network.cpp b/modules/juce_core/native/juce_curl_Network.cpp
index 8781712c18..7e6518f739 100644
--- a/modules/juce_core/native/juce_curl_Network.cpp
+++ b/modules/juce_core/native/juce_curl_Network.cpp
@@ -130,7 +130,7 @@ public:
     //==============================================================================
     bool setOptions()
     {
-        const String address = url.toString (! isPost);
+        auto address = url.toString (! isPost);
 
         curl_version_info_data* data = curl_version_info (CURLVERSION_NOW);
         jassert (data != nullptr);
@@ -144,7 +144,7 @@ public:
         if (! requestHeaders.endsWithChar ('\n'))
             requestHeaders << "\r\n";
 
-        String userAgent = String ("curl/") + data->version;
+        auto userAgent = String ("curl/") + data->version;
 
         if (curl_easy_setopt (curl, CURLOPT_URL, address.toRawUTF8()) == CURLE_OK
             && curl_easy_setopt (curl, CURLOPT_WRITEDATA, this) == CURLE_OK
@@ -166,11 +166,10 @@ public:
 
             // handle special http request commands
             bool hasSpecialRequestCmd = isPost ? (httpRequest != "POST") : (httpRequest != "GET");
+
             if (hasSpecialRequestCmd)
-            {
                 if (curl_easy_setopt (curl, CURLOPT_CUSTOMREQUEST, httpRequest.toRawUTF8()) != CURLE_OK)
                     return false;
-            }
 
             if (curl_easy_setopt (curl, CURLOPT_HEADERDATA, this) != CURLE_OK
                 || curl_easy_setopt (curl, CURLOPT_HEADERFUNCTION, StaticCurlHeader) != CURLE_OK)
@@ -178,7 +177,7 @@ public:
 
             if (timeOutMs > 0)
             {
-                long timeOutSecs = ((long) timeOutMs + 999) / 1000;
+                auto timeOutSecs = ((long) timeOutMs + 999) / 1000;
 
                 if (curl_easy_setopt (curl, CURLOPT_CONNECTTIMEOUT, timeOutSecs) != CURLE_OK
                     || curl_easy_setopt (curl, CURLOPT_LOW_SPEED_LIMIT, 100) != CURLE_OK
diff --git a/modules/juce_core/network/juce_IPAddress.cpp b/modules/juce_core/network/juce_IPAddress.cpp
index 2b38499faa..333208066f 100644
--- a/modules/juce_core/network/juce_IPAddress.cpp
+++ b/modules/juce_core/network/juce_IPAddress.cpp
@@ -162,11 +162,10 @@ String IPAddress::getFormattedAddress (const String& unformattedAddress)
 {
     jassert (unformattedAddress.contains (":") && ! unformattedAddress.contains ("::")); // needs to be an unformatted IPv6 address!
 
-    String portString = unformattedAddress.fromFirstOccurrenceOf ("]", false, true);
-    String addressString = unformattedAddress.dropLastCharacters (portString.length()).removeCharacters ("[]");
+    auto portString    = unformattedAddress.fromFirstOccurrenceOf ("]", false, true);
+    auto addressString = unformattedAddress.dropLastCharacters (portString.length()).removeCharacters ("[]");
 
-    StringArray tokens;
-    tokens.addTokens (addressString, ":", String());
+    auto tokens = StringArray::fromTokens (addressString, ":", {});
 
     int numZeros = 0;
     int numZerosTemp = 0;
@@ -175,7 +174,7 @@ String IPAddress::getFormattedAddress (const String& unformattedAddress)
 
     for (int i = 0; i < tokens.size(); ++i)
     {
-        String t = tokens.getReference (i);
+        const auto& t = tokens.getReference (i);
 
         if (t.getHexValue32() == 0x0000)
         {
@@ -212,21 +211,23 @@ String IPAddress::getFormattedAddress (const String& unformattedAddress)
     if (numZeros > 1)
     {
         if (numZeros == tokens.size())
+        {
             addressString = "::,";
+        }
         else
         {
-            String zeroString = isFirst ? String ("0") + String::repeatedString (":0", numZeros - 1)
-                                        : String::repeatedString (":0", numZeros);
+            auto zeroString = isFirst ? "0" + String::repeatedString (":0", numZeros - 1)
+                                      : String::repeatedString (":0", numZeros);
 
             addressString = addressString.replaceFirstOccurrenceOf (zeroString, ":");
 
             if (isLast)
-                addressString += String (":");
+                addressString << ':';
         }
     }
 
     if (portString.isNotEmpty())
-        addressString = String ("[") + addressString + String ("]") + portString;
+        addressString = "[" + addressString + "]" + portString;
 
     return addressString;
 }
@@ -249,7 +250,7 @@ bool IPAddress::operator!= (const IPAddress& other) const noexcept
 #if (! JUCE_WINDOWS) && (! JUCE_ANDROID)
 static void addAddress (const sockaddr_in* addr_in, Array<IPAddress>& result)
 {
-    in_addr_t addr = addr_in->sin_addr.s_addr;
+    auto addr = addr_in->sin_addr.s_addr;
 
     if (addr != INADDR_NONE)
         result.addIfNotAlreadyThere (IPAddress (ntohl (addr)));
diff --git a/modules/juce_core/time/juce_PerformanceCounter.h b/modules/juce_core/time/juce_PerformanceCounter.h
index 506a490442..7076ad1f75 100644
--- a/modules/juce_core/time/juce_PerformanceCounter.h
+++ b/modules/juce_core/time/juce_PerformanceCounter.h
@@ -131,7 +131,7 @@ private:
             doSomething();
         }
 
-        Logger::writeToLog (String ("doSomething() took ") + String (timeSec) + "seconds");
+        Logger::writeToLog ("doSomething() took " + String (timeSec) + "seconds");
     }
 
     @param resultInSeconds The result of the measurement will be stored in this variable.
diff --git a/modules/juce_dsp/frequency/juce_FFT.cpp b/modules/juce_dsp/frequency/juce_FFT.cpp
index 8077185857..2dfe9eb40c 100644
--- a/modules/juce_dsp/frequency/juce_FFT.cpp
+++ b/modules/juce_dsp/frequency/juce_FFT.cpp
@@ -601,14 +601,14 @@ struct FFTWImpl  : public FFT::Instance
 
       #if ! JUCE_DSP_USE_STATIC_FFTW
        #if JUCE_MAC
-        const char* libsuffix = "dylib";
+        auto libName = "libfftw3f.dylib";
        #elif JUCE_WINDOWS
-        const char* libsuffix = "dll";
+        auto libName = "libfftw3f.dll";
        #else
-        const char* libsuffix = "so";
+        auto libName = "libfftw3f.so";
        #endif
 
-        if (lib.open (String ("libfftw3f.") + libsuffix))
+        if (lib.open (libName))
       #endif
         {
             Symbols symbols;
diff --git a/modules/juce_gui_basics/native/juce_ios_FileChooser.mm b/modules/juce_gui_basics/native/juce_ios_FileChooser.mm
index b0b474b79a..4b479c9a50 100644
--- a/modules/juce_gui_basics/native/juce_ios_FileChooser.mm
+++ b/modules/juce_gui_basics/native/juce_ios_FileChooser.mm
@@ -181,7 +181,7 @@ private:
             extension = fallbackExtension;
 
         if (extension.isNotEmpty())
-            filename += String (".") + extension;
+            filename += "." + extension;
 
         return filename;
     }
diff --git a/modules/juce_gui_extra/native/juce_mac_WebBrowserComponent.mm b/modules/juce_gui_extra/native/juce_mac_WebBrowserComponent.mm
index 6ac198150b..83909cb392 100644
--- a/modules/juce_gui_extra/native/juce_mac_WebBrowserComponent.mm
+++ b/modules/juce_gui_extra/native/juce_mac_WebBrowserComponent.mm
@@ -119,13 +119,12 @@ private:
     {
         if ([frame isEqual: [sender mainFrame]] && error != nullptr && [error code] != NSURLErrorCancelled)
         {
-            String errorString (nsStringToJuce ([error localizedDescription]));
-
+            auto errorString = nsStringToJuce ([error localizedDescription]);
             bool proceedToErrorPage = getOwner (self)->pageLoadHadNetworkError (errorString);
 
             // WebKit doesn't have an internal error page, so make a really simple one ourselves
             if (proceedToErrorPage)
-                getOwner(self)->goToURL (String ("data:text/plain;charset=UTF-8,") + errorString);
+                getOwner (self)->goToURL ("data:text/plain;charset=UTF-8," + errorString);
         }
     }
 
diff --git a/modules/juce_opengl/opengl/juce_OpenGLHelpers.cpp b/modules/juce_opengl/opengl/juce_OpenGLHelpers.cpp
index a6c93365dd..2d379203dc 100644
--- a/modules/juce_opengl/opengl/juce_OpenGLHelpers.cpp
+++ b/modules/juce_opengl/opengl/juce_OpenGLHelpers.cpp
@@ -100,7 +100,7 @@ String OpenGLHelpers::translateVertexShaderToV3 (const String& code)
 
             for (int p = code.indexOf (0, "attribute "); p >= 0; p = code.indexOf (p + 1, "attribute "))
             {
-                output += code.substring (last, p) + String ("layout(location=") + String (--numAttributes) + ") in ";
+                output += code.substring (last, p) + "layout(location=" + String (--numAttributes) + ") in ";
 
                 last = p + 10;
             }
diff --git a/modules/juce_osc/osc/juce_OSCSender.cpp b/modules/juce_osc/osc/juce_OSCSender.cpp
index dc98d8b993..c9cff521d3 100644
--- a/modules/juce_osc/osc/juce_OSCSender.cpp
+++ b/modules/juce_osc/osc/juce_OSCSender.cpp
@@ -677,7 +677,7 @@ public:
 
         beginTest ("OSC message with multiple arguments");
         {
-            OSCMessage outMessage ("/test/four_args", 42, 0.5f, String ("foo"), String ("bar"));
+            OSCMessage outMessage ("/test/four_args", 42, 0.5f, "foo", "bar");
 
             OSCOutputStream output;
             output.writeMessage (outMessage);
@@ -721,7 +721,7 @@ public:
 
             OSCMessage inMessage = inBundle[0].getMessage();
 
-            expectEquals (inMessage.getAddressPattern().toString(), String ("/test/one_arg"));
+            expectEquals (inMessage.getAddressPattern().toString(), "/test/one_arg");
             expectEquals (inMessage.size(), 1);
             expectEquals (inMessage[0].getInt32(), 42);
         }
@@ -730,7 +730,7 @@ public:
         {
             OSCMessage outMessage1 ("/test/empty");
             OSCMessage outMessage2 ("/test/one_arg", 42);
-            OSCMessage outMessage3 ("/test/four_args", 42, 0.5f, String ("foo"), String ("bar"));
+            OSCMessage outMessage3 ("/test/four_args", 42, 0.5f, "foo", "bar");
 
             OSCBundle outBundle;
             outBundle.addElement (outMessage1);