diff --git a/src/synth/fluid_synth.c b/src/synth/fluid_synth.c
index 6a0b280f..45e2a72f 100644
--- a/src/synth/fluid_synth.c
+++ b/src/synth/fluid_synth.c
@@ -3800,6 +3800,16 @@ int
 fluid_synth_write_float(fluid_synth_t *synth, int len,
                         void *lout, int loff, int lincr,
                         void *rout, int roff, int rincr)
+{
+    return fluid_synth_write_float_LOCAL(synth, len, lout, loff, lincr, rout, roff, rincr, fluid_synth_render_blocks);
+}
+
+int
+fluid_synth_write_float_LOCAL(fluid_synth_t *synth, int len,
+                        void *lout, int loff, int lincr,
+                        void *rout, int roff, int rincr,
+                        int (*block_render_func)(fluid_synth_t *, int)
+                       )
 {
     int i, j, k, l;
     float *left_out = (float *) lout;
@@ -3825,7 +3835,7 @@ fluid_synth_write_float(fluid_synth_t *synth, int len,
         if(l >= synth->curmax)
         {
             int blocksleft = (len - i + FLUID_BUFSIZE - 1) / FLUID_BUFSIZE;
-            synth->curmax = FLUID_BUFSIZE * fluid_synth_render_blocks(synth, blocksleft);
+            synth->curmax = FLUID_BUFSIZE * block_render_func(synth, blocksleft);
             fluid_rvoice_mixer_get_bufs(synth->eventhandler->mixer, &left_in, &right_in);
 
             l = 0;
diff --git a/src/synth/fluid_synth.h b/src/synth/fluid_synth.h
index 0b9758ba..b649bcf3 100644
--- a/src/synth/fluid_synth.h
+++ b/src/synth/fluid_synth.h
@@ -216,6 +216,11 @@ int fluid_synth_set_gen2(fluid_synth_t *synth, int chan,
 int
 fluid_synth_process_LOCAL(fluid_synth_t *synth, int len, int nfx, float *fx[],
                     int nout, float *out[], int (*block_render_func)(fluid_synth_t *, int));
+int
+fluid_synth_write_float_LOCAL(fluid_synth_t *synth, int len,
+                        void *lout, int loff, int lincr,
+                        void *rout, int roff, int rincr,
+                        int (*block_render_func)(fluid_synth_t *, int));
 /*
  * misc
  */
diff --git a/test/test_synth_process.c b/test/test_synth_process.c
index bdae3bbd..0e2bff71 100644
--- a/test/test_synth_process.c
+++ b/test/test_synth_process.c
@@ -8,18 +8,17 @@
 // static const int CHANNELS=16;
 enum { SAMPLES=1024 };
 
+static int smpl;
+
 int render_one_mock(fluid_synth_t *synth, int blocks)
 {
-    static int smpl;
-    
+
     fluid_real_t *left_in, *fx_left_in;
     fluid_real_t *right_in, *fx_right_in;
 
     int i, j;
 
-    int nfxchan = fluid_synth_count_effects_channels(synth),
-        nfxunits = fluid_synth_count_effects_groups(synth),
-        naudchan = fluid_synth_count_audio_channels(synth);
+    int naudchan = fluid_synth_count_audio_channels(synth);
 
     fluid_rvoice_mixer_get_bufs(synth->eventhandler->mixer, &left_in, &right_in);
     fluid_rvoice_mixer_get_fx_bufs(synth->eventhandler->mixer, &fx_left_in, &fx_right_in);
@@ -37,27 +36,61 @@ int render_one_mock(fluid_synth_t *synth, int blocks)
     return blocks;
 }
 
-int render_and_check(fluid_synth_t* synth, int number_of_samples, int offset)
+int process_and_check(fluid_synth_t* synth, int number_of_samples, int offset)
 {
     int i;
     float left[SAMPLES], right[SAMPLES];
     float *dry[1 * 2];
     dry[0] = left;
     dry[1] = right;
-    memset(left, 0, sizeof(left));
-    memset(right, 0, sizeof(right));
-    
+    FLUID_MEMSET(left, 0, sizeof(left));
+    FLUID_MEMSET(right, 0, sizeof(right));
+
     TEST_SUCCESS(fluid_synth_process_LOCAL(synth, number_of_samples, 0, NULL, 2, dry, render_one_mock));
-    
+
     for(i=0; i<number_of_samples; i++)
     {
-        TEST_ASSERT(left[i]==i+offset);
-        TEST_ASSERT(right[i]==i+offset);
+        TEST_ASSERT(left[i]==offset);
+        TEST_ASSERT(right[i]==offset);
+        offset++;
     }
-    
-    return i+offset;
+
+    return offset;
 }
 
+
+int write_and_check(fluid_synth_t* synth, int number_of_samples, int offset)
+{
+    int i;
+    float buf[2*SAMPLES];
+    FLUID_MEMSET(buf, 0, sizeof(buf));
+
+    // one buffer, interleaved writing
+    TEST_SUCCESS(fluid_synth_write_float_LOCAL(synth, number_of_samples, buf, 0, 2, buf, 1, 2, render_one_mock));
+
+    for(i=0; i< 2*number_of_samples; i+=2)
+    {
+        TEST_ASSERT(buf[i+0] == offset);
+        TEST_ASSERT(buf[i+1] == offset);
+        offset++;
+    }
+
+    FLUID_MEMSET(buf, 0, sizeof(buf));
+
+    // "two" buffers, planar writing
+    TEST_SUCCESS(fluid_synth_write_float_LOCAL(synth, number_of_samples, buf, 0, 1, buf, SAMPLES, 1, render_one_mock));
+
+    for(i=0; i< number_of_samples; i++)
+    {
+        TEST_ASSERT(buf[i+0] == offset);
+        TEST_ASSERT(buf[i+SAMPLES] == offset);
+        offset++;
+    }
+
+    return offset;
+}
+
+
 // this test should make sure that sample rate changed are handled correctly
 int main(void)
 {
@@ -66,19 +99,32 @@ int main(void)
     fluid_settings_t *settings = new_fluid_settings();
     TEST_ASSERT(settings != NULL);
 
-//     TEST_SUCCESS(fluid_settings_setint(settings, "synth.audio-channels", CHANNELS));
-//     TEST_SUCCESS(fluid_settings_setint(settings, "synth.audio-groups", CHANNELS));
-
     synth = new_fluid_synth(settings);
     TEST_ASSERT(synth != NULL);
 
-    off = render_and_check(synth, 100, off);
-    off = render_and_check(synth, 200, off);
-    off = render_and_check(synth, 300, off);
-    off = render_and_check(synth, 1000, off);
-    off = render_and_check(synth, 900, off);
-    off = render_and_check(synth, 800, off);
-    
+    off = process_and_check(synth, 100, off);
+    off = process_and_check(synth, 200, off);
+    off = process_and_check(synth, 300, off);
+    // next statement should not result in a call to render_one_mock() and therefore not increase the static "smpl" var
+    off = process_and_check(synth, 0, off);
+    off = process_and_check(synth, 1000, off);
+    off = process_and_check(synth, SAMPLES, off);
+    off = process_and_check(synth, 900, off);
+    off = process_and_check(synth, 800, off);
+    off = process_and_check(synth, FLUID_BUFSIZE, off);
+
+    // currently it is not possible to call different rendering functions subsequently
+    off = smpl;
+
+    off = write_and_check(synth, 100, off);
+    off = write_and_check(synth, 200, off);
+    off = write_and_check(synth, 300, off);
+    off = write_and_check(synth, 0, off);
+    off = write_and_check(synth, 1000, off);
+    off = write_and_check(synth, SAMPLES, off);
+    off = write_and_check(synth, 900, off);
+    off = write_and_check(synth, 800, off);
+    off = write_and_check(synth, FLUID_BUFSIZE, off);
 
     delete_fluid_synth(synth);
     delete_fluid_settings(settings);