diff --git a/beat.py b/beat.py
index 61a9c82..7e1d73a 100644
--- a/beat.py
+++ b/beat.py
@@ -172,14 +172,15 @@ class RegularBeatFinder:
         # evaluate mean absolute errors for all frequencies
         freqs, freq_errs = self._get_opt_ibi_freq_2(fs, act_ibis, debug_i)
         # bias with f_hint - once we know the beat freq, make it more likely for it to be found everywhere
-        nf, f1, f2 = RegularBeatFinder.num_freqs, RegularBeatFinder.range_f2, RegularBeatFinder.range_f1
-        bias = gauss(
-            nf,
-            (f_hint - f1) / (f2 - f1) * nf,
-            RegularBeatFinder.f_bias_width * nf
-        )
-        freqs_bias = 1.0 / (np.max(bias)+bias)  # make 'f_hint' at most 2x more likely -- (1+bias) if normalized
-        freq_errs *= freqs_bias
+        if f_hint is not None:
+            nf, f1, f2 = RegularBeatFinder.num_freqs, RegularBeatFinder.range_f2, RegularBeatFinder.range_f1
+            bias = gauss(
+                nf,
+                (f_hint - f1) / (f2 - f1) * nf,
+                RegularBeatFinder.f_bias_width * nf
+            )
+            freqs_bias = 1.0 / (np.max(bias)+bias)  # make 'f_hint' at most 2x more likely -- (1+bias) if normalized
+            freq_errs *= freqs_bias
         #
         if debug_fe:
             plt.figure(figsize=(8,2))
diff --git a/song.py b/song.py
index c8c4703..017ad78 100644
--- a/song.py
+++ b/song.py
@@ -33,8 +33,12 @@ class SongBeatDetector:
 
         seg_sl = int(SongBeatDetector.SEGMENT_SLICE_LEN_SEC * fsd)
 
-        self.zds = []
+        self.zds = self._estimate_segments(debug_fe_idx=debug_fe_idx)
+        return self.zds
 
+    def _estimate_segments(self, f_hint=None, debug_fe_idx=None):
+        zds = []
+        fsd = self.fsd
         # for each segment
         for i in np.arange(self.i_seg.shape[0]-1):
             i1, i2 = self.i_seg[i], self.i_seg[i+1]
@@ -52,12 +56,12 @@ class SongBeatDetector:
                     debug_fe = i1 <= debug_fe_sidx < i2
                 else:
                     debug_fe = False
-                zdd = self._process_slice(j1, j2, m, seg_sl, sig_slice, debug_fe=debug_fe)
-                self.zds.append(zdd)
+                zdd = self._process_slice(j1, j2, m, seg_sl, sig_slice, f_hint=f_hint, debug_fe=debug_fe)
+                zds.append(zdd)
 
-        return self.zds
+        return zds
 
-    def _process_slice(self, j1, j2, m, seg_sl, sig_slice, debug_fe=False):
+    def _process_slice(self, j1, j2, m, seg_sl, sig_slice, f_hint=None, debug_fe=False):
         """
         :param j1: lower index into 'sig_slice'
         :param j2: upper index into 'sig_slice'
@@ -100,7 +104,7 @@ class SongBeatDetector:
 
         # nice-to: optimize phase, (maybe iteratively, optimize phase and freq each)
         bf = RegularBeatFinder()
-        fb, ne = bf.find_beat(fsd, ssf_zxings, debug_fe=debug_fe, debug_i=None)
+        fb, ne = bf.find_beat(fsd, ssf_zxings, f_hint=f_hint, debug_fe=debug_fe, debug_i=None)
         if debug_fe: plt.title(f'regular-beat placement error (mae), slice [{j1}:{j2}]')
         # mae is unnurmalized here, as returned from RegularBeatFinder._get_opt_ibi_freq_2()
         zdd.update({