diff --git a/src/spectrogram.c b/src/spectrogram.c
index 8bde5cb..82525e5 100644
--- a/src/spectrogram.c
+++ b/src/spectrogram.c
@@ -147,25 +147,53 @@ get_colour_map_value (float value, double spec_floor_db, unsigned char colour [3
 } /* get_colour_map_value */
 
 
+/*
+** Read the sample data for a analysis frame from the sound file, turning
+** multi-channel audio into mono by mixing the channels equally.
+**
+** The parameters say which window, out of the N we will process, we are
+** reading the audio for; this is mapped to the centre of the window being
+** positioned at the first sample of the file or the last one, with any
+** samples beyond the edges of the audio file being filled with silence.
+**
+** In an attempt to reduce interference-pattern artifacts, we reduce the
+** 1-sample-period time jitter caused by rounding exact windor position to
+** a sample interval, by interpolating between adjacent samples.
+** There is no evidence that this makes any visible improvement.
+**
+*/
 static void
 read_mono_audio (SNDFILE * file, sf_count_t filelen, double * data, int datalen, int indx, int total)
 {
-	sf_count_t start ;
+	double start;		 /* Start of window, in units of 1/samplerate */
+	sf_count_t index;        /* "start" rounded left to sample index */
+	double point_what;       /* Fractional part of "start", 0.0 to 0.999* */
 
 	memset (data, 0, datalen * sizeof (data [0])) ;
 
-	start = (indx * filelen) / total - datalen / 2 ;
+	start = (indx * filelen * 1.0) / total - datalen / 2.0 ;
+
+	index = (sf_count_t) floor (start);
+	point_what = start - floor (start);
 
-	if (start >= 0)
-		sf_seek (file, start, SEEK_SET) ;
+	if (index >= 0)
+		sf_seek (file, index, SEEK_SET) ;
 	else
-	{	start = -start ;
+	{	int missing = -index ;
 		sf_seek (file, 0, SEEK_SET) ;
-		data += start ;
-		datalen -= start ;
+		data += missing ;
+		datalen -= missing ;
 		} ;
 
-	sfx_mix_mono_read_double (file, data, datalen) ;
+	if (point_what == 0.0)
+		sfx_mix_mono_read_double (file, data, datalen) ;
+	else
+	{	int i;
+		sfx_mix_mono_read_double (file, data, datalen + 1) ;
+		for (i=0; i<datalen; i++)
+			data[i] = data[i] * (1.0 - point_what) +
+			          data[i + 1] * point_what;
+		} ;
 
 	return ;
 } /* read_mono_audio */
diff --git a/src/spectrum.c b/src/spectrum.c
index d936943..f3d5a81 100644
--- a/src/spectrum.c
+++ b/src/spectrum.c
@@ -18,15 +18,30 @@ spectrum *
 create_spectrum (int speclen, enum WINDOW_FUNCTION window_function)
 {	spectrum *spec ;
 
-	spec = calloc (1, sizeof (spectrum) + ((2 + 2 + 2 + 1) * speclen + 1) * sizeof (double)) ;
+	spec = calloc (1, sizeof (spectrum));
+	if (spec == NULL)
+	{	printf ("%s : Not enough memory.\n", __func__) ;
+		exit (1) ;
+		} ;
 
 	spec->wfunc = window_function ;
 	spec->speclen = speclen ;
 
-	spec->time_domain = spec->data ;
-	spec->window = spec->time_domain + 2 * speclen ;
-	spec->freq_domain = spec->window + 2 * speclen ;
-	spec->mag_spec = spec->freq_domain + 2 * speclen ;	/* mag_spec has values from [0..speclen] inclusive */
+	/* mag_spec has values from [0..speclen] inclusive for 0Hz to Nyquist.
+	** time_domain has an extra element to be able to interpolate between
+	** samples for better time precision, hoping to eliminate artifacts.
+	*/
+	spec->time_domain = calloc (2 * speclen + 1, sizeof(double));
+	spec->window      = calloc (2 * speclen, sizeof(double));
+	spec->freq_domain = calloc (2 * speclen, sizeof(double));
+	spec->mag_spec    = calloc (speclen + 1, sizeof(double));
+	if (spec->time_domain == NULL ||
+	    spec->window      == NULL ||
+	    spec->freq_domain == NULL ||
+	    spec->mag_spec    == NULL)
+	{	printf ("%s : Not enough memory.\n", __func__) ;
+		exit (1) ;
+		} ;
 
 	spec->plan = fftw_plan_r2r_1d (2 * speclen, spec->time_domain, spec->freq_domain, FFTW_R2HC, FFTW_MEASURE | FFTW_PRESERVE_INPUT) ;
 	if (spec->plan == NULL)