diff --git a/py_bombcell/bombcell/default_parameters.py b/py_bombcell/bombcell/default_parameters.py
index 345d3eb..0fab9ca 100644
--- a/py_bombcell/bombcell/default_parameters.py
+++ b/py_bombcell/bombcell/default_parameters.py
@@ -43,6 +43,7 @@ def get_default_parameters(
         "saveAsTSV": True,  # save outputs as a .tsv file, useful for using phy after bombcell
         "unit_type_for_phy": True,  # save a unit_type .tsv file for phy
         "ephysKilosortPath": str(kilosort_path),  # path to the KiloSort directory
+        "joblib_backend_preference": "processes", # 'processes' OR 'threads
 
         ## Duplicate spike parameters
         "removeDuplicateSpikes": False,
diff --git a/py_bombcell/bombcell/extract_raw_waveforms.py b/py_bombcell/bombcell/extract_raw_waveforms.py
index 719f345..aba67fa 100644
--- a/py_bombcell/bombcell/extract_raw_waveforms.py
+++ b/py_bombcell/bombcell/extract_raw_waveforms.py
@@ -524,7 +524,12 @@ def extract_raw_waveforms(
                 all_spikes_idxs[i, : len(clus_spike_times[i])] = clus_spike_times[i]
                 all_spikes_idxs[i, len(clus_spike_times[i]) :] = np.nan
 
-        all_waveforms = Parallel(n_jobs=-1, verbose=10, mmap_mode="r", max_nbytes=None)(
+        try:
+            prefer = param["joblib_backend_preference"]
+        except KeyError:
+            param["joblib_backend_preference"] = "processes"
+            prefer = param["joblib_backend_preference"]
+        all_waveforms = Parallel(n_jobs=-1, verbose=10, mmap_mode="r", max_nbytes=None, prefer=prefer)(
             delayed(process_a_unit)(
                 raw_data,
                 spike_width,