Port the surge phaser to sst-effects

include/sst/effects/Chorus.h

@@ -0,0 +1,24 @@
+/*
+ * sst-effects - an open source library of audio effects
+ * built by Surge Synth Team.
+ *
+ * Copyright 2018-2023, various authors, as described in the GitHub
+ * transaction log.
+ *
+ * sst-effects is released under the GNU General Public Licence v3
+ * or later (GPL-3.0-or-later). The license is found in the "LICENSE"
+ * file in the root of this repository, or at
+ * https://www.gnu.org/licenses/gpl-3.0.en.html
+ *
+ * The majority of these effects at initiation were factored from
+ * Surge XT, and so git history prior to April 2023 is found in the
+ * surge repo, https://github.com/surge-synthesizer/surge
+ *
+ * All source in sst-effects available at
+ * https://github.com/surge-synthesizer/sst-effects
+ */
+
+#ifndef INCLUDE_SST_EFFECTS_CHORUS_H
+#define INCLUDE_SST_EFFECTS_CHORUS_H
+
+#endif // SURGE_CHORUS_H

include/sst/effects/EffectCore.h

@@ -241,6 +241,8 @@ template <typename FXConfig> struct EffectTemplateBase : public FXConfig::BaseCl
         width.multiply_block(S, FXConfig::blockSize >> 2);
         sdsp::decodeMS<FXConfig::blockSize>(M, S, L, R);
     }
+
+    static constexpr int slowrate{8}, slowrate_m1{slowrate - 1};
 };
 } // namespace sst::effects::core